issue 681 MarkerLabel creation and MarkerParentModel is gone

This resolves issue #681.

MarkerLabel:
- Any options property of label" " will make the gMarker a MarkerLabel.
- this gets rid of the need for isLabel entirely and the LabelDirective can be deleted.

MarkerParentModel:
- removed so that the main marker logic is all in one place MarkerChildModel.

Before merging I need to remove the directive scope of "=isLabel" and delete the Label directive and models.

@gitnik @cthrax 
_async.waitOrGo expects a promise to be returned. This allows a destroyed  windows model clean up, and then delay any recreation until it is ready. This is a trickle effect to window/windows as well. IE Window or Windows waits on Marker/Markers to be ready.