Preliminary verion of a port of Gef4 MVC to GWT

To achieve the port to GWT, dependencies to eclipse command API had to be removed,
meaning the command classes had to be removed from GEF4 MVC, due to non supported
classes by GWT use in the eclipse command API.

GEF4 MVC also made heavy use of PropertyChangeListener that is not supported by GWT. All code
using PropertyChange has been removed and replaced with GWT Events.
Preliminary version of a GEF4 MVC exampel running on GWT.
Added containment examples to the geometry example and reorganize code.
Added main example demo app.
Add test module for geometry.
Update gwt dependency to 2.6.0 and gef4