Switch to Account manager, syncadapter & contentprovider.

Changes in short:
- Cleanup unused imports
- Rewritten auto-sync (Works now on the background)
- Prefs user/password has been moved to the safe account manager
- Updated androidmanifest for the requied permissions
- Added/Removed strings
- Removed old settings
- Updated login screen (use accountmanager)
Merge pull request #181 from ratan12/Account_Manager

Account manager, syncadapter & contentprovider.