fix NPE in SimpleWorker cleanup
use android-logger
add vtm-jeo
add examples
update target sdk
add gradle
update Indoor example
Merge branch 'jeo'
gradle: update jeo config
jeo: desktop indoor example
gradle: dont build parallel by default
app++
libgdx api changes
android logger.properties
change url, mod_tile now provides CORS
remove MapTile.loader field for GWT
rewrite VelocityTracker to work with varying frequency samples

- improve fling behaviour
- should fix #49
serious refactor: TileLoader:

- no more duplication of TileLoaders for GWT ->
- decouple loadTile() from TileDataSource completed() call
- all TileDataSource MUST call completed(success) in any case now
fix: ElementLayers, make sure setFrom() clears previous items
refactor: extract theme RulerBuilder from Rule