Drag and drop

Added back in the functionality for dragging and dropping from the sidebar.  Also added a little wiggle animation when you mouse over something you can drag :^]

Haven't tested it with anything except for photos and markers, but seems to work with those.  Also edited some formatting in a couple files, which makes it look like I've changed the entire file - sorry about that!

PROTIP: just click on the first commit (Adding functionality for...) below, and compare the code there.  It was pre-reformatting, which screwed up the diff