Add MSSQL support, unify and fix "before" & "after" sql config, review most RDBMS configs

The highlight of this PR and the main structural and functional changes include:

changes how top level and per-query options apply to CLI invocations
changes how before and after applied (top level and per-query)
introduction of new execute named query section which is used when executing statements with ST: Execute and friends (Execute All File, Execute Query from History, etc)
since above-mentioned items affect configuration for each RDBMS, review each of them, when possible fix, add new or missing functionality.

This one is a somewhat lengthy pull request, but as you can see it is for a good reason.

Here is a more detailed list of things that got fixed or improved in this PR:

Ensure before and after runs on all commands. Make sure that before and newly introduced after sql in cli_options settings is added to each command (if configured on the top level) as well as introduce optional per command before and "afterwhich are run in addition mainbeforeandafter`.
Change how top level and per-query options work. The new concept of applying options is: top-level options are applied to all CLI invocations (all queries). In addition to top-level options each named query options are appended.
New named query execute is introduced, which helps to better control which options are applied when the user executes the query using ST: Execute or ST: Execute All File.
Now all named query formatting is done via str.format(), therefore all instances of %s in template strings got replaced with "{0}", with back-patch support (i.e. %s should still work for those users who have it on their own user config, which overrides the default one)
Use the encoding supplied in connection settings when writing to standard input and reading from standard output of CLI command
General review of each RDBMS config to ensure it works with newly introduced changes
Refactor SQLToolsAPI/Connection.py

These RDBMS got some improvements.

[PostgreSQL] Added trailing semicolon - in case user would add something to before or after sql section the default config (multi-statement SQL) would work just fine
[Oracle] Add support for functions & procedures completions as well as getting and functions & procedures source code (both top level and those in packages).
[Oracle] Add support for quoted table and column names
[Oracle] Add ability to configure NSL_LANG to match the server encoding
[MySQL] Use utf8 encoding by default when invoking MySQL CLI (which matches the encoding set in default connection config)
[MSSQL] Add support for ST : Explain Plan

Fixes #120

mtxr / SublimeText-SQLTools