checkboxes and radio buttons:
- do not change color on hover when disabled
- are focusable and checkable be keyboard again. This uses a little
trick where the real checkbox is hidden under the artificial
checkbox. That way it has the same position and therefore it
works even in containers with overflow set.
https://fedorahosted.org/freeipa/ticket/4217
Reviewed-By: Adam Misnyovszki <amisnyov@redhat.com>
Tests modified to comply with PEP8 rules with exception of rule E501 (long lines).
Done by autopep8 tool and 2 manual modifications.
https://fedorahosted.org/freeipa/ticket/3744
