Edited Issue: Designer: Can't select EF6 for model-first [1111]

__Steps:__
1. New Project
2. Add new ADO.NET Entity Data Model item
3. Empty model
4. Update/Generate

__Unexpected result:__
EF6 is disabled and notification reads, "Your project references an older version of Entity Framework. To use the latest version, exit this wizard and upgrade before performing this action."

__Workaround:__
Remove reference to System.Data.Entity before invokig Generate/Update