Add Simpler Dev14 support

Also remove incorrect copy local.

The solution should now build and install on VS 11, 12, and 14, and the build from any version should work on any other version.

Microsoft.VisualStudio.TestPlatform.ObjectModel v11 must still exist on disk, as noted in the Wiki.

I believe that the unit tests will only work in VS2012, and that that was always true.