Add references to all dlls in ~./kpm/packages for temp ASP.NET vNext fix

This is definitely in a "Works on My Machine, No Guarantees This Won't Kill Your Puppy"&trade; kind of state. From what I can tell, the `CSharpProject` constructor that I'm invoking this method in will only be called in the solution-less case, so hopefully this won't affect people using OmniSharp for standard .NET projects. 

I'm boiling the ocean and just grabbing anything that exists in the kpm/packages directory. That could cause all kinds of problems depending on the state of your packages cache, not to mention being slow, but it works for the demo I want to do, since I can just clean the directory out prior to demoing and guarantee that there's nothing else in there that I don't want.

Also discovered that it doesn't seem to like the `~` notation for the user directory, so I used the SpecialDirectories enum to find it instead.

Hope you can make use of this, my apologies if it introduces too many bad side effects!