Add in base64 image encoding to build system and move images over to use it

Maybe I'm missing something but I'm not sure why leaflet needed to be hacked to make retina icons work, if we just pass the url for retina to the normal and not default icon it should work properly.

I would move the draw images over but since those are setup in the plugin they are not built in right now.

This should fix #441 and any others dealing with images failing to load.

I think it makes sense to do this and remove external dependencies for most of the script.