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.
I would write: We use reflection because the server side should not depend on gwt-servlet nor gwt-dev.