Bug 7628 - Required format is not enforced for Patron Categories

Bug 7628 - Required format is not enforced for Patron Categories

Enforces category code with allowed characters only.

Test plan:

- Before applying patch, create a category code like Test+

- Try to delete category with this code -> does not work

- Apply patch

- Try to create category with code containg other characters than letters, numbers, - and _

- Result: You are not allowed to do so, appropriate message pops up

Signed-off-by: David Cook <dcook@prosentient.com.au>