Enhance support for Markers

[steveszc]

There are quite a few Marker properties, events, and methods that are present in the Google Maps API but absent from the g-maps-marker component. Its probably not feasible to fully re-implement the Google Maps API for Markers, but the following list seems like a good place to start, and many of these API features such as drag events and opacity are implemented on other components in this addon, such as the g-maps-polyline component.

• Complex Icon: Currently a url may be provided as a marker's icon property to set a custom marker image, but there is no support for an icon object containing a url, anchor, labelOrigin, origin, scaledSize, or size. Some of these properties may be necessary when using a custom marker image. For instance, a custom marker may need to be anchored to the map in the center of the icon, rather than the default bottom-center. (edit: this is supported but undocumented)
• animation
• anchorPoint
• Opacity
• draggable/dragStart/drag/dragEnd

[steveszc]

I'll be working on the Complex Icon support in the next couple weeks, PR will be forthcoming.