Reminder to deprecate the old extension framework for later removal

Deprecate the old extension framework so that it can be removed in a later release (i.e, 8.0).

Per conversation 1/6/2012 B. LaFond & D. Florian:

We need to advise the user NOT to use the old extension model. Maybe a new first page in the wizard contributor saying to use the new framework.
1) New Model Wizard Changes
2) user has "existing" extension model and wants to EDIT. What do we do? Anything?
3) User selects the Properties Editor and the "Change Model Extension" dialog. Could we intercept that and WARN them too? guess we would still let them edit the extension model but also need to "warn" them in this scenario also. A Notification Listener could check for edits on an Extension Metamodel (URI) and pop up a warning. Could have the toggle "Dont' show this again" kinda thingee
4) maybe change the label from "Model Extension" to "Model Extension (deprecated)" in the New Model wizard
5) Maybe put a watermark on diagram background or throw some Text in the upper left hand corner (Extension Model is Deprecated: Use MED instead)