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

The path in project.properties will require local overriding. I tried directly
referencing the SDK with ${sdk.dir} but the build fails with an absolute path
to a library.

To satisfy dependencies, import the following other projects from i2p.i2p into
the same Eclipse workspace as i2p.android.base:
i2p_sdk       - core/java/
i2p_router    - router/java/
i2ptunnel     - apps/i2ptunnel/java/
BOB           - apps/BOB/
addressbook   - apps/addressbook/
jetty         - apps/jetty/
ministreaming - apps/ministreaming/java/

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