- Migrated I2PActivityBase and subclasses to Fragment
- Added new MainActivity with navigation drawer to handle Fragments
- Added MainFragment to navigation drawer

Code compiles, installs and runs. Known bugs created:
- Some buttons now fail (can't use an Intent with a Fragment)
  -> Migrate usage of Intents to Fragment transactions
- New install/upgrade dialogs are commented out
  -> Migrate old Dialogs to DialogFragments