Bug 7628: Escape '+' characters for categorycode

Bug 7628: Escape '+' characters for categorycode

uri escape the following characters:
    &, @, /, ;, :, =, +, ? and $

Signed-off-by: Marc Veron <veron@veron.ch>
Test and sign off second patch (independently from first patch).

Added categories like '+zwoelf' or '? Test' before applying the patch.
Deletion was not possible.

After applying patch deletion is possible, patch works as expected.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>