Android application

This is a placeholder merge request to share my initial implementation on an Android app.

It currently compiles, links and loads fine, but for some reason it does not load any tiles.

On debug build I only get "source 0: 0" on the screen.

Anyone know what the problem might be?

It uses https://github.com/ljbade/mapnik-packaging/commits/android-app as that has some needed fixes.

It will also need the patches mentioned:
for libuv - https://github.com/mapnik/mapnik-packaging/issues/163
for boost - https://github.com/mapnik/mapnik-packaging/issues/162

Finally this includes fixes for:
https://github.com/mapbox/mapbox-gl-native/issues/332
https://github.com/mapbox/mapbox-gl-native/issues/331