CTest: add command line option to run the tests listed in the given file

This patch adds the new ctest command line option --run-from which can be used to run only the tests listed in the given file. The testnames must match exactly, no regexps or something. The listed tests can be filtered with a regexp using -R

This is actually not a merge request, but a review request. I'm not too happy with the name of the command line option. As it is, it seems to combine properly with the other filtering options, but I'm not sure. Also, I don't know how to add a test for that functionality.

I'm happy about comments.