Bug 7380: Rename filter to avoid confusion

Bug 7380: Rename filter to avoid confusion

The branchcode and categorycode parameter names are too common and are
confusing.
To remove the ambiguity, this patch renames them with branchcode_filter
and categorycode_filter.

Test plan:
1/ Go on the patron home page (members-home.pl)
2/ Fill the library and category dropdown list in the header search
3/ The patron result list appears and the filters (on the right) are
correctly set with what you have selected.
Make sure the ones in the header are also correctly selected.
4/ Click on a patron
5/ On the patron detail page (moremember.pl), the dropdown lists in the
header are not preselected.

Signed-off-by: Nicole Engard <nengard@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>