Final clean-up

Functionality is unaltered while the PR focuses on:

- Minimize static use
- Use composition where possible
- Rename some classes to be more expressive
- Limit BagOStuff/MediaWiki dependency to GlossaryCache only
- Added MwDBSQLStoreIntegrationTest to test a "real" DB/Store integration

Change-Id: Id0e0e1c19afc3aceb06fe75f2d5892cd2a065f34