update slf4j android
improve MapRenderer

- add functions to bind shared VBOs
- make MapView field non-static
flip MarkerLayer items over date-line
add MarkerLayer example
fix possible concurrent modification
add Color.rainbow()
funky color path example
update README
merge Vec2 class into OBB2D
fix PausableThread:

set 'mPausing = false' on thread after pause, not on call to proceed()
as the thread may already have been stopped in which case awaitPausing
will loop forever -- short: dont use thread utility classes you havent
written yourself :)
fix themes
synchronize clearing TileLayer on its TileRenderer instead of global MapRenderer.drawlock
fix: Color.fade()
fix deadlock on AndroidMap<>Viewport:

- on GL-Thread:
MapRenderer.draw()->MapAnimator->update()->AndroidMap.updateMap
                    [sync: Viewport       [sync: AndroidMap ]]
- on Mainloop:
AndroidMap.redrawMapInternal()->updateLayers()->Viewport.getMapPosition()
[sync:AndroidMap                               [sync:Viewport]]

... no need to sync on AndroidMap
fix: clear previous tile jobs when changing theme
cancel TileLoader job when thread shouldPause

- handle Exceptions in PbfTileDataSource, cleanup in finally{}
refactor TextRenderer, sync MapTile in Label-Thread
set MapTile.STATE_CANCEL when tile is cleared

in TileManager.jobCompleted clear tile when tile state is CANCEL
Merge branch 'wip_sync'
add MapRenderer.animate() to trigger animations on GL-Thread