xunit and nunit work, MsTest still needs some work

I put three projects for MsTest, nUnit and xunit.net. I don't know much about the JSON thing, so I'm less than capable for creating an example solution for it.

By the way, I had troubles generating good trx file for MsTest (that's why in pickles repository it isn't substituted yet). I investigated the case and discovered that my mstest console runner does not write properties (<Property> tags) into trx report when ran, while the original pickles example has them and they're used by the parser.

I guess the examples for mstest would work if I knew how to generate trc files with properties.