Throw in drag and drop example from raphaelgwt

Just a copy and paste.
There's a slight code-reorg mixed into this too, sorry.
.gitignore
Remove GreetingService

Superfluous GWT bootstrap/demo code.
Try to tidy things up a bit.

Since I'm modifying DraggableCircle to taste, I might as well import
it to our source tree
Play with PathBuilder a bit.