Commented Task: Designer: Consider scenarios where both EF5 and EF6 are installed [1321]

It is possible for a project to reference both EF4/EF5 (SDE.dll) and EF6. We should consider either supporting these scenarios in the designer, ensuring the latest version is always used when possible and failing gracefully when it is not.
Comments: Related work item: https://entityframework.codeplex.com/workitem/1178