add geoson tile source

based on patch by: Yang (apachemaven)
- use jackson-core for stream parsing
- rewrite tags, this way one can use the same the for different data
add geojson tilesource examples

- add OsmLanduseJsonTileSource
- add layers for buildings and water areas
gradle: geojson examples
gwt: geojson tilesource
gwt: test map layers
theme: fix river width below zoom=12
android-example: use VectorTileLayer instead of OsmTileLayer
desktop example
handle Point and MultiPoint