Rewrite CachedOsmTileRetriever

[abhinayagarwal]

CachedOsmTileRetriever has multiple issues:

1. CacheThread has an indefinite while loop. The deactivate() which is supposed to break the while loop is never called.
2. In Osm license #52, CachedOsmTileRetriever is being updated to a non-static class. This will lead to having different instances of CacheThread writing to the same cache directory. If the PR is merged, this needs to be fixed as well.