Added merge stream and exclude filter.
Added a constructor to add a drawable to a marker
Merge pull request #197 from Macjon/master

I've added a constructor to set the marker image
Merge pull request #198 from OsmSharp/exclusive_filter

Added merge stream and exclude filter.
Added two new stream filters.
Fixed bug in PBFOsmStreamSource: Resetting should also clear object cache.
Merge remote-tracking branch 'upstream/master'