refactor: PbfTileDataSource -> UrlTileDataSource
use LwHttp.Buffer to set limit on InputStream
refactor: add TileLayer.initLoader()

- need to initialize worker thread after (super) class is constructed
add ITileDataSink.setTileImage(bitmap) to interface
fix: always initialize TileManager
add isValid() to Bitmap interface
simplify UrlTileDataSource initialization
cleanup
new BitmapTileLayer implementation
settings: export slf4j
Merge branch 'unify_tilesources'
update app