[with patch; needs work] Separate resource for @interact

Good, works, but has one problem, which is that it creates a serious security vulnerability. It needs code like this or something like in the Worksheet_eval Resource:

        if owner != '_sage_':
            if W.owner() != self.username and not (self.username in W.collaborators()):
               return InvalidPage(msg = "can't evaluate worksheet cells", username = self.username\
)

Once this is resolved, it will get a positive review.

It might also be nice if there were a comment that explains why we are creating this new resource. E.g., "make code cleaner"? "because it will be needed later for something else that is planned?"