Add Framework Version to the XML

[rprouse]

There have been small additions to the XML generated by the framework over time and tools like the Visual Studio Adapter have come to rely on some of those new attributes being present. The adapter project has requested that we expose the framework version so that they can drop back to the old XML parser for older versions of the framework.

This will add the existing environment element to test-suite when exploring tests. The environment element contains the element framework-version.

This also adds framework-version to the start-suite XML event.