Added support for Awesome Markers Plugin

Hi, 

I've added support to awesome-markers plugin.
I also updated the example marker update example, but as I do not know how to deal with icon images in bootstrap, the image inside the icon does not appear. I you know what to include in the html file do it for me please.
If you play with the example you will be able to use two awesome icons and the drag will continue to be functional.

To do it I've added a Helper class to deal with plugins and make the code more readable. Is this structure OK?

Jaume.