Merge branch 'rule_refactor'
example: cleanup
add SyncPool.clear()
dispose textures at end of each frame
update README
use one TexturePool per BitmapTileLayer

- dispose textures onDetach()
increase java PermSize in gradle.properties
Merge branch 'texture_pool_dispose'
Extracts configurable networking layer.

* Extracts HttpEngine interface.
* Uses LwHttp as default networking client.
* Implements alternate networking client using OkHttp.
Tests OkHttp integration
create HttpEngine instances for each loader thread
example: testing OkHttp
move tests to separate project
Fixes HttpEngine tests
okhttp: use tileSource.getTileUrl()