OPEN - task 79: Improve Object, Process and State figures 
https://github.com/vainolo/Object-Process-Programming/issues/issue/79

Figures which have a name now implement the OPMNamedElementFigure
interface, and it is used in all operations (refresh, direct edit, etc).

Removed most functionality from OPMThingEditPart, passed it on to the
children. Will later unify if needed.