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 
big difference here is that parentScope is gone as all that was really needed was the keys (strings or functions) which link to the underlying model data. So in Marker a keys are basically mocked up to point to identical properties (coords:"coords", icon:"icons") and key names. Where as Markers it could be anything (coords:"self", coords:object, coords:function,..etc).