Allow the addition of MSTest Runner as a capability

Quote from user:

We are trying to get our automated building to stop using the IDE for compilation and testing, because of the reasons listed in Paul Duvall's book Continuous Integration:

• each developer may be using a different IDE, and there may be configuration differences between installs;
• CI must be done without human intervention, and therefore should be runnable from a build script separate from the IDE.

It will be great if we can add the MSTest.exe as a capability outside of the Visual studio IDE similar to the way NunitRunner is added as a capability.