Make GQ server side not depends on gwt-servlet not gwt-dev

Adding org.json dependency since we depend on it, and 2.7
uses a rebased version of android.json. We will have this
dependency in snapshot until we replace json usage in server
side, but we have to remove before releasing gquery.
My idea is to change with elemental.json since everything in vaadin is now it right now and it is a light weight implementation. Probably I'll copy those few classes in the gquery.jar instead of make it depend on gwt-elemental nor android.json etc. I have experience with it, so when I have a couple of hours I'll do very soon