Refactor createTile

• Implement tiles updating, to be able to display new data without full redraw

• Implement tiles loading failing method, and make cleanup on 'tilesloaded' (close #34).

  Note: before this MR images visibility was enforced. Now it is leaved as is (i.e. inherited), so the tile appears at once as whole, and under some conditions may be delayed by one of sublayers.

• Implement more robust sublayers handling, provide basic sample to add KmlLayer (close #94)

• In order to facilitate dynamic options change - make tile cache to consider such map options as type, style, google layers (close #129)