Remove GlobalSettingsProvider interface and replace w/ GlobalSettingsProvider class, the class is the old IniSettingsProvider class.

Fixing unit tests, includes environment creation/destruction to UnitTestCase base class + ability to override environment in UnitTestCase.

The container now uses IniFileChain, which means it doesn't need the Config object anymore.

Initially we considered dropping the `ini` config, but the current stance is we keep `config.ini.php` because it's a user friendly config.