Bug 32886: Set focus for cursor to Code when adding a new restriction

Bug 32886: Set focus for cursor to Code when adding a new restriction

This patch adds the "focus" class to the form for defining a new patron
restriction so that the cursor focus is automatically added.

To test, apply the patch and go to Administration -> Patron restrictions
-> New restriction.

The cursor should automatically move to the "Code" input field.

Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>