Temporary; will eventually be in an about menu in settings

The navigation drawer has been (mostly) migrated to link to Activities instead
of Fragments. Only Activities can be searched via the inbuild Android search
function, which uses Intents.

Side-effect: some constant strings are now public

- 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

- Update release notes
- Lower log levels
- Spelling fixes on settings page

Screenshots could be found at: http://meeh.i2p/android/ui/2/

- Update README.txt and release notes
- Add irc.killyourtv.i2p to IRC list
- Use new buildI2PTunnelJar target
- LogWriter cleanup