Merge pull request #1026 from jails/bug/mongo-relations

Fixes some issues related to mongo relations.
Adding alternative database connections for testing.
Adding test for switching databases.
Remove selection of database before each query for MySql.
Cleaning up whitespace.
Fixing creation of test databases for CI.
Split and fix creation of test database for postgres CI.
Set DELETE method on Curl socket
Merge pull request #1034 from fountainhead-solutions/bug/curl-delete-header

Set DELETE method on Curl socket
Updating multiple database test.
Adding test for switching DB on distinct models.
Removing explicit connection switching from test.

This should address the original question correctly.
Adding documentation to tests.
Removing alternative test database for SQLite.

Adding note about usage of in memory databases.
Adding skips to tests when two in memory database are in use.
Merge pull request #1033 from davidpersson/use-database

Removing `USE DATABASE` upon each query for MySql adapter.
Disable channel and email notifications; GitHub provides enough feedback.
Optimize git clone in CI script.
Use multiple script feature in CI.
Use env variables directly for CI.
Install mongo extension only when needed.