Bug 5002: Display messages on adding/deleting patron category

Bug 5002: Display messages on adding/deleting patron category

There are no messages on adding and deleting patron category.
If an error occurs and the data is not inserted, the interface does not
alert the user.

This patch adds a message block to alert the user if something wrong
happened.

Test plan:
1/ Create a patron category PATCAT. You should get a confirmation
message.
2/ Try to create another patron category with the same code. You should
get an error message
3/ Delete the patron category PATCAT. You should get a confirmation
message.

Confirm there is no regression on this form (try update an existing
patron category too).

Followed test plan, works as expected.
Signed-off-by: Marc Veron <veron@veron.ch>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>