Bug 21854: Use template plugin to display category description

Bug 21854: Use template plugin to display category description

Rather than getting the description in the script and passing, we should
just use the tmeplate plugin to get the description from the category
code.

To test:
1 - Find a patron, note their category
2 - Visit Tools - Batch patron modification
3 - Enter barcode of patron above
4 - Note category does not show in the display of patrons to be modified
5 - Apply patch
6 - Reload the page, note the patron category displays
7 - Modify the patron (anything but category)
8 - Check that category still diplays correctly in results

Signed-off-by: Pierre-Marc Thibault <pierre-marc.thibault@inLibro.com>
Signed-off-by: Andreas Roussos <arouss1980@gmail.com>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>