Simplify Multi-Targting

Currently (VS2015 Update 2 with .NET Core RC2 Tools Preview 1) targeting more than one framework is hard.
- You have to manually find the version of the dependency that works on that framework.
- You have to manually make sure you have access to the same types, even though they may be different dependencies between frameworks.
- When a type is available in one framework but not the other you have to find what dependency you have to add to make it available in the other (though https://packagesearch.azurewebsites.net/ helps with that)