Some administrative commands need to be added to `show @@ help`

dble version：
5.6.29-dble-9.9.9.9-a5491f6-20181123014546
preconditions ：
no
configs：

schema.xml

rule.xml

server.xml

steps：
step1.
expect result：
1.contains all administrative commands

real result：
1.

mysql> show @@help;
+---------------------------------------------+-----------------------------------------------------------------------+
| STATEMENT                                   | DESCRIPTION                                                           |
+---------------------------------------------+-----------------------------------------------------------------------+
| select @@VERSION_COMMENT;                   | Show the version comment of dble                                      |
| show @@time.current                         | Report current timestamp                                              |
| show @@time.startup                         | Report startup timestamp                                              |
| show @@version                              | Report Server version                                                 |
| show @@server                               | Report server status                                                  |
| show @@threadpool                           | Report threadPool status                                              |
| show @@database                             | Report databases                                                      |
| show @@datanode [where schema = ?]          | Report dataNodes                                                      |
| show @@datasource [where dataNode = ?]      | Report dataSources                                                    |
| show @@datasource.synstatus                 | Report datasource data synchronous                                    |
| show @@datasource.syndetail where name=?    | Report datasource data synchronous detail                             |
| show @@datasource.cluster                   | Report datasource galary cluster variables                            |
| show @@processor                            | Report processor status                                               |
| show @@command                              | Report commands status                                                |
| show @@connection                           | Report connection status                                              |
| show @@cache                                | Report system cache usage                                             |
| show @@backend                              | Report backend connection status                                      |
| show @@session                              | Report front session details                                          |
| show @@connection.sql                       | Report connection sql                                                 |
| show @@sql                                  | Report SQL list                                                       |
| show @@sql.high                             | Report Hight Frequency SQL                                            |
| show @@sql.slow                             | Report slow SQL                                                       |
| show @@sql.large                            | Report the sql witch resultset larger than 10000 rows                 |
| show @@sql.condition                        | Report the query of a specific table.column set by reload query_cf    |
| show @@sql.resultset                        | Report BIG RESULTSET SQL                                              |
| show @@sql.sum                              | Report  User RW Stat                                                  |
| show @@sql.sum.user                         | Report  User RW Stat                                                  |
| show @@sql.sum.table                        | Report  Table RW Stat                                                 |
| show @@heartbeat                            | Report heartbeat status                                               |
| show @@heartbeat.detail where name=?        | Report heartbeat current detail                                       |
| show @@sysparam                             | Report system param                                                   |
| show @@syslog limit=?                       | Report system log                                                     |
| show @@white                                | Report server white host                                              |
| show @@directmemory=1 or 2                  | Report server direct memory usage                                     |
| show @@command.count                        | Report the current number of querys                                   |
| show @@connection.count                     | Report the current number of connections                              |
| show @@backend.statistics                   | Report backend node info                                              |
| show @@backend.old                          | Report old connections witch still alive after reload config all      |
| show @@binlog.status                        | Report the current GTID of all backend nodes                          |
| show @@help                                 | Report usage of manager port                                          |
| show @@cost_time                            | Report cost time of query , contains back End ,front End and over all |
| show @@thread_used                          | Report all bussiness&reactor thread usage                             |
| show @@dataNodes where schema=? and table=? | Report the data nodes info of a table                                 |
| show @@algorithm where schema=? and table=? | Report the algorithm info of a table                                  |
| switch @@datasource name:index              | Switch dataSource                                                     |
| kill @@connection id1,id2,...               | Kill the specified connections                                        |
| stop @@heartbeat name:time                  | Pause dataNode heartbeat                                              |
| reload @@config                             | Reload basic config from file                                         |
| reload @@config_all                         | Reload all config from file                                           |
| reload @@metadata                           | Reload metadata of tables                                             |
| reload @@sqlslow=                           | Set Slow SQL Time(ms)                                                 |
| reload @@user_stat                          | Reset show @@sql  @@sql.sum @@sql.slow                                |
| reload @@query_cf[=table&column]            | Reset show @@sql.conditiont                                           |
| rollback @@config                           | Rollback all config from memory                                       |
| offline                                     | Change Server status to OFF                                           |
| online                                      | Change Server status to ON                                            |
| file @@list                                 | List all the file in conf directory                                   |
| file @@show filename                        | Show the file data of specific file                                   |
| file @@upload filename content              | Write content to file                                                 |
| log @@[file=? limit=? key=? regex=?]        | Report logs by given regex                                            |
+---------------------------------------------+-----------------------------------------------------------------------+
60 rows in set (0.01 sec)

supplements：
1.the missing part

dryrun pause @@DataNode RESUME show @@pause show @@slow_query_log; enable @@slow_query_log; disable @@slow_query_log; show @@slow_query.time; reload @@slow_query.time show @@slow_query.flushperiod; reload @@slow_query.flushperiod show @@slow_query.flushsize reload @@slow_query.flushsize create database @@dataNode ='dn......' check @@metadata check full @@metadata



/label ~BUG

actiontech / dble

Some administrative commands need to be added to `show @@ help` #852