Visual studio runner

I wanted a Test Adapter for Visual Studio (issue #26) and I saw there was an open branch. In the last commit it said that running the tests ended in a crash. I wanted to know why, so I looked at it and kind of ended up fixing the crash.

The test adapter now runs, but there are still issues (discrepancies between the tests that are discovered and the tests that are run).

Also, for easy debugging, I added a VSIX project :smile: