Config refactoring

***DO NOT MERGE***

These changes are intended to go out on the devboxes next week, to prepare them for the new deploy tools.

The main change is that all environments go through the same top level config/LocalSettings.php file. The wgWikiaDatacenter variable comes from the app/LocalSettings.php file which is the new top level entry point for all environments.

@Wikia/platform-team @justinmhunter