Bug 30874: Replace categoryname

Bug 30874: Replace categoryname

== Test plan ==
1. Apply all patches
2. Create a new patron in a given category
   => Form show the dropdown with the selected category
3. Edit again
   => Value is kept
4. Edit a category to give it specific values for: messaging prefs,
   password strength/length, can be guarantee
5. Edit the patron, change the category, and confirm that the different
   limitation are correctly applied.

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>