Fix geopackage tiles example
Validate TileCursor constructor parameters
Bounds.intersection should keep projection
Guard TileCursor against empty bounds.  Add getEmpty() method to check if it covers no tiles
When empty TileCursor will return a blank raster.  ImageTileLayer should handle this gracefully
The TileGenerator can now generate tiles that intersect a bounds
Add Vector Tile support to the tile module. Supported formats include geojson, mvt, and pbf
Fix groovydocs