Issue 417

This fixes #417 

One or nunit test projects may be entered on the command line, possibly intermixed with assemblies. All results are combined and reported together.

Tests for DefaultTestRunnerFactory and InProcessTestRunnerFactory have been added.
The Any CPU build configuration got added back in, can you edit your configurations and delete it? Having one configuration makes the command line msbuild easier because we don't have to specify which to use.