Add toggle between Tests and TestCaseFilter in vstest command

[Dmitry Tretyakov]

VsTest does not support both filters simultaneously, so we need to introduce toggle between them:
https://msdn.microsoft.com/en-us/library/jj155796.aspx?f=255&MSPPError=-2147217396

Warning: The /Tests command line option cannot be used with the /TestCaseFilter command line option.