A simple graph model for the first iteration.

The idea is just to create a simple GEF editor around this mock graph
model of nodes and connections, and when the GEF editor is in place,
replace this model with something from Neo4J.
Putting a GEF editor with a dummy model in a view.

Used the code example from
http://www.programcreek.com/2013/03/eclipse-gef-tutorial/
to construct the model and the view.

This wasn't really what I wanted, though.  I would like a GEF editor,
and not a GEF View.