Nunitlite runner in separate assembly

**For Discussion, don't merge yet**

This PR is intended to help with the discussion on the dev list about supporting self-executing tests.

I have removed the Runner directory entirely from the framework. Since it was only present in nunitlite, this eliminates one more key difference in the two frameworks.

The nunitlite tests are still runnable but now reference both framework and runner assemblies. If desired, we could also make the runners executable on some platforms, allowing them to be used in a more traditional way.
Damn that Mixed Plaforms, Win32 and x64 configurations. They keep getting re-added in every time someone adds a project to the solution. That might be a reason to drop the C++ projects from the solution. I think they are the ones causing it, although the x86 agent may also.

I will clean this up after the merge. No reason to hold up on it.