Get the Android app building and linking to native libraries.

Changes:
  * Update `build.sh` to properly build, link, and install
    cross-compiled libraries.
  * Update `.gitignore` to ignore generated build files and git repos.
  * Update `update.sh` to clone libuuid.
  * Update `Android.mk` to tell the NDK to link with the generated
    libraries
  * Add the JNI interface.

TODO:
  * Update docs.
  * Remove hard-coded paths to "/home/shancat/".
  * Fix the app crashing on toggle.
  * Update Travis build script.

Note: This will not build.