reset MapElement layer to default
refactor TileClipper

- fix: TileClipper check len<6 before len==0
fix: SimplifyDP handling of 'multi' geometries
cleanup: SimplifyVW
cleanup: OBB2D
cleanup: LineTexLayer
close TileSource on VectorLayer detach
fixme: re-init TileSet when count is zero..
submit update task on PathLayer.setGeom()
add MapPosition accessors
vtm-android: disable check-gl-error flags
add TaskQueue interface to Map

- change AsyncTask to be able to post on main-thread
- rename Task.run() -> go()
API: make Rule members public
API: remove setBackgroundMap, add setBaseMap(TileLayer)
API: allow changing number of TileLoader threads
use inverted MeshLayer debug colors
dbg: VectorTileLayer
no need to pre-calc BoundingBox hashcode
s3db: disable postprocess mode

- seems old mali having issues with dependent texture reads..
- add bypass shader for testing
s3db: more material colors