Add thumbnail storage support

- Display thumbnails in history view
- History Content provider joins tables with PageImages
- Page Images saved when a history entry is made. Will change
  in the future to get the PageImage data with the mobileview
  request itself, and avoid the extra request.
- Add 'upsert' feature to the Content Persisters

Change-Id: I65c94258f5f1908edee6d6ceb8137570b0feb3a4
Run the history clearer every day

Change-Id: I341f7d7ecf01bf1a0f83b33ddd21f73c93cb75ef