* Adds possibility to have custom annotation pins on static map. This resolves#1889.
* Removes wrong example for map annotations and adds some annotations to correct map example. #1889
* Static map node now uses specific property block to get annotation views.
* Changes self to strongSelf inside of the snapshotters completion block.
* MapNode: Adds statement in documentation.
* MapNode: Block for annotation view/image now returns UIImage and center offset is returned in inout param.
* MapNode and map example: Fixes from review.
* MapNode example: Gets image directly from custom annotation, without creating annotation view.
