Fix bug 827836 (VenusDDRIT failure)

Change the default of skipAssemblyReferences to true.
Fix unit tests
Change the build system.

Use VisualStudioVersion to decide what to build:
- When VisualStudioVersion is empty, set it to "10.0".
- When VisualStudioVersion == "10.0", build vsix for dev10 & dev11
- When VisualStudioVersion == "11.0", build vsix for dev11
- When VisualStudioVersion == "12.0", build vsix for dev12
Merge branch 'master' into dev14
Fix unit tests
add updatesourceforvs2014
Fix dev14 build
Fix hint path for VisualStudio.Shell.dll
Fix hintpath
Build improvement:
- Create VisualStudioUIWrapper, change all xaml files to reference this wrapper
- Make vsixmanifest VS version specific
- Move stuff in VisualStudio11 to VisualStudio

Conflicts:
	NuGet.sln
	src/VsExtension/NuGetPackage.cs
	src/VsExtension/VsExtension.csproj
Add project TeamFoundataionServer14
Update build.proj for dev14
Merge branch 'master' into dev14
Fix a merge problem
Merge branch '2.8.1' into dev14
Disable package restore tests on Dev14
Add VS14 specifi dlls
Add expected exception ObjectDisposedException to MockServer.
Fix functional test InstallLatestVersionWorksCorrectlyWithPrerelease so that
it does not rely on packages from nuget.org.
Further fix of functional tests.