Android: Added README and new scripts, and updated build-script to generate deployable package

1. The Android helper scripts have been moved to /cjdns/contrib/android/cjdroid.
2. An installer script has been added to help deploy the whole setup correctly.
3. An init script has been added to start the daemon during the boot process.
4. A README.md has been added to explain how things work and what to do.
5. The build script has been updated to allow variable repositories and branches.
6. The build script now generates a compressed package that includes the install script, all the helper scripts and the freshly generated cjdroute binary.