Add nice shortcuts to CLI

[betodealmeida]

$ pydruid
> SHOW TABLES;
TABLE_NAME
----------------
foo
bar
baz
COLUMNS
SCHEMATA
TABLES
> SHOW SCHEMAS;
SCHEMA_NAME
------------------
druid
INFORMATION_SCHEMA
> DESC foo;
COLUMN_NAME        ORDINAL_POSITION  COLUMN_DEFAULT    IS_NULLABLE    DATA_TYPE
---------------  ------------------  ----------------  -------------  -----------
__time                            0                    NO             TIMESTAMP
count                             1                    NO             BIGINT
location                          2                    YES            VARCHAR
aaaaaa                            3                    YES            VARCHAR
bbbbbb                            4                    YES            VARCHAR
sum_cccccccccc                    5                    NO             FLOAT
>

[betodealmeida]

I'm planning to add support for DROP TABLES, but that requires extra work since it needs to communicate with the coordinator instead of the broker. For the Pinot connector I added an option to pass multiple hosts (server and broker), we can do the same thing for Druid.

[mistercrunch]

@betodealmeida the broker may be able to handle some of the coordinator api. I'm not 100% sure but remember hearing that before. We should get to the bottom of it, it'd be great if Superset could also talk only to the broker.