Remove stock recovery

The app needs a recovery capable of flashing more than one zip in a row
(twrp or cwm-based ones)
Remove unused method
Updaters workout

- Added PaServer (untested, still doesn't return updates)
- Updaters check next server is there's no updates in the current one
- Reworked rom and gapps updater classes as they shared a lot of code
- Removed hardcoded string
Fix duplicate string