Bug 25867: Database update for changing existing frameworks

Bug 25867: Database update for changing existing frameworks

This updates the descriptions for 952$a und $b in all existing
frameworks, if the English description hasn't been changed since
installing Koha.

To test:
- Look at your item edit form or on the MARC tab
  for the descriptions shown for $a and $b for any framework
- Note the descriptons say '... location'
- Change one or more using the frameworks.
- Run the database update
- Verify only the unchanged ones have been updated

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>