Adds base ContentProvider, removes unused apis
Adds test to show imgur is flexible wrt extensions.

- As long as the extension is jpg, jpeg, gif or png, imgur doesn't care. It won't take 'bmp' though.
- Adds the thumbnail loading too
Moves heightRatio logic out of the view, back to adapter
fixes CS...ANTONIO
Removes invalid test
Adds Persistor which can bulk insert when we get a new gallery.

- It doesn't currently like update though for some reason
Fixes according to PR review, adds inefficient update db call.

- want to do upsert or insertorreplace but the sqliteprovider doesn't support.
- instead, doing a query to check if the record exists, updating if so, else adding to the list of records to bulk insert.
Merge pull request #20 from ataulm/persist_galleries

responds to code review
Fixed according to comments