Add contains functionality in gnults.py

[SaurabhK122]

#443

[terriko]

Out of curiousity, was there a reason you changed the return in the "is" section?

[SaurabhK122]

I found it easy to work with version_info as a dictionary, because while checking if version is not unknown we also need to know whether is_or_contains is null or not, that's why

[terriko]

You don't actually need it for the is_or_contains check because you're returning if it "is" and the code below will never be reached, but I think you're right that it's nicer to read the way you've got it.