Add support for port/socket

[josh4trunks]

Logic is added to handle specified port / unix file socket for database connections.
For example, the following now all work as expected...

ZM_DB_HOST=localhost
ZM_DB_HOST=REMOTE_HOST:1234
ZM_DB_HOST=localhost:/path/to/non-default.sock

For the API to work in the same manner, this PR must be merged. #1470

Fixes #901

[josh4trunks]

@SteveGilvarry @connortechnology This is ready for review/merge.

[josh4trunks]

@knnniggett @connortechnology
Looking at 58b5194, is the plan moving forward to have the Perl database connection in two places?
If so I can adjust my PR accordingly.

[connortechnology]

This is going to be left for the next release.

Ideally, there should be only 1 place.

[josh4trunks]

Ok, so no mysql port/socket support till 1.30.1? (I don't know the numbering)

Or did you mean no database connection merging? I can adjust this PR so it works either way, the logic is pretty simple.

[josh4trunks]

Closed in favor of #1498