Bug 33673: Change "global system preferences" to "system preferences"

Bug 33673: Change "global system preferences" to "system preferences"

The Koha Community normally refers to "global system preferences"
as just "system preferences".

This updates the staff interface and other occurences to refelect
this, including:
- Administration > Global system preferences and the description
- Patrons > [a patron] > More > Set permissions > Manage Koha
  system settings > Manage global system preferences
  (manage_sysprefs)
- The installer files and the database (permissions table)

Test plan:
1. Note that in the staff interface "Global system preferences"
   is dispalyed in two places:
   1.1 Administration: Go to Administration. There is a section
       called "Global system preferences" with a description
       and a search box.
   1.2 User permissions: View the details for a patron > More >
       Set permissions > expand 'Manage Koha system settings' >
       scroll down to 'Manage global system preferences
       (manage_sysprefs)'
2. Apply the patch.
3. Update the database.
4. Revisit the pages in step 1 - these should now show as
   "System prefereneces" or "system preferences" as appropriate.
5. Sign off!

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Magnus Enger <magnus@libriotech.no>
I agree with this change, consistency is good. As far as I can see
this patch cathes all the occurrences of "global".
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>