Add UTFGrid and CartoDB Map API Support

Add suppor for layers UTFGrid and CartoDB Map API 

### Features
##### CartoDB

* Tiles layer
* UTFGrid layer
* Combine Tiles and UTFGrid for interactivity.

##### UTFGrid

* UTFGrid as overlay layer.
* Mouse events for interactivity.

##### Legend
* Add metadata.

### Fixes
* Fix error #447