Migrate to GWT 2.7 beta 1

`UiBinderGenerator` had compilation errors when changing to GWT 2.7b1, so I rebased it onto gwt/trunk 
I knew we were overriding UiBinder, but I thought it was fixing some bug not adding functionality.

I can't really see the benefit of this just to not use (provided = true).  Add to that that it might break when GWT changes.

I think move it to a different module for the people that might like it and maybe even a different project.