Bug 7919: FIX the "all" categories method

The C4::Category->all method must return fields from the categories
table only.
Without this patch, there is 2 "categorycode" values, the second one is
sometimes undef (if no branch limitation).

same for the GetBorrowercategoryList routine (some category codes are
undefined)

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Liz Rea <liz@catalyst.net.nz>
Signed off for also fixing problems with patron searching noted by Katrin.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Problems fixed by this patch include:
- on patron search result list the category description is shown again
- it's possible to limit a patron search to a patron category again

All tests pass.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Merge branch 'bug_7919' into 3.12-master