GWT Updates

This pull request addresses the following issues.

ROO-3353: Make GAE and GWT version properties 
ROO-3352: setAccetableValues(Collection collection) method is still added to EditViews when field is marked read-only in proxies. 
ROO-3211: Modify the inheritance chain of activities and views in order to increase flexibility. 
ROO-3208: setEntityPickerValues method not being added to View interface in EditActivityWrapper 
ROO-3204: Use existing renderers in mobile list views rather than defining new ones 
ROO-3179: Better organize the scaffolded views in a GWT application 
ROO-3178: If a user adds a field to an unmanaged edit view, do not add it to the managed edit view