Move role page definitions into module

Move role page definitions into module
The function gets redefined every time group_data gets called. I see that roles being in the function's scope is a handy shortcut, but I think it would benefit from being more explicit. To that end, I think it should be at the module level with the signature `_remove_page(roles, group, pages)` and pages should always be a list.

Then, if a group is not in roles, or if a page is not in a group's pages, warnings should be logged so we know that our data is out of sync.