Have extra options when adding optional recipes to modify aspects of the recipe

[brianmoose]

@dschwen suggested that it would be nice to be able to have extra options when adding optional recipes to a PR.
For example, he had a minor change to fix a memory leak in a single test in the valgrind heavy recipe which takes 4+ hours to complete. It would be nice if there was a way to specify an --re to the run_tests so that we wouldn't have to run all of them.
This same idea could be used in other places as well.