fixes #1715 and no i18n tests
missed something
made the check_copy_relations check a bit smarter by taking superclasses in account

fixes #1723
clears url caches
fixes testsuite
Readd viewsitelink CSS class to page change_form template

This is needed for finer control over the link's styling.
2.4.1 - authors, changelog and version bump
never directly use the User model, always call get_user_model first