Bug 17221: (follow-up) Orphan comma in shelf browser

Bug 17221: (follow-up) Orphan comma in shelf browser

This further improves the display if no location or no
collection has been set. Example output:

Browsing Centerville shelves, Collection: Non-fiction

Also changes 'Collection code' to 'collection' and takes
care of additional spaces before the comma.

To test:
- Make sure your OpacShelfBrowser pref is set to "Show"
- Search for a record with items and callnumbers in your OPAC
- "Browse shelf"
- Navigate back and forth, verify the information showing on
  top of the list is correctly formatted
- Try different combinations for the following prefs:
  - ShelfBrowserUsesCcode
  - ShelfBrowserUsesHomeBranch
  - ShelfBrowserUsesLocation
- Verify the display is always nicely formatted

Note: fixing capitalization here is tricky, as it also
depends on what was displayed before. If you have no
homebranch, you would want "Shelving...", if you have one
we'd like "shelving...". Left as I found it for now.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>