Xamarin Android project support

I'd like to reap the benefits of file globbing and convert a Xamarin Android project (
``).

Even with no other changes, as soon as I add `monoandroid71`, Visual Studio no longer allows me to start an emulator.

I can do the full csproj conversion, including `monoandroid71`, and it builds fine.

If I do the full csproj conversion but I leave out the `` element it does not restore and reference NuGet packages via ``, and it also adds a few `The referenced component 'System.Drawing' could not be found.` compiler warnings and this compiler warning:

> "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\Microsoft.CSharp.targets" cannot be imported again. It was already imported at "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.CSharp.targets (38,5)". This is most likely a build authoring error. This subsequent import will be ignored."

I can fix the warnings but I need the package restore to work.

So, due to a few hours' testing, it appears that I can't have globbing without ``. I can't have `` without moving from NuGet-only project.json to ``. I can't move to `` without `monoandroid71`. I can't add `` without losing the ability to run the project.

I know that support for this may be aways out on your roadmap, but what can I do now to achieve globbing without messing up the ability to press F5 to debug in an emulator?

(@onovotny you're usually pushing the envelope here. Have you tried this?)