Bug 11827: Make "Cancel Rating" translatable in jQuery rating plugin

Bug 11827: Make "Cancel Rating" translatable in jQuery rating plugin

- Make the "Cancel rating" text translatable (and change
  capitalization to conform to Koha coding guidelines)
- Improve the two other messages to use formatted strings
  instead of concatenation.
- Use the exact same text for the "your rating" text, so it
  only appears once in the po-file.

Test plan:

1. See that the "Cancel rating" -text doesn't appear in
   po/xx-YY-opac-bootstrap.po
2. Note how there's two versions of the your rating -text
   ("your rating: %s, " and "your rating:") in the po-file
3. Apply patch
4. Update the xx-YY translation
5. Check the po-file. It should now contain the "Cancel rating"
   and a single "your rating: %s, "
6. Translate those texts, and update & install the language.
7. Go to the OPAC detail page of a biblio, and check the
   rating texts.
8. Hovering over the rating minus -sign should show the translated
   "Cancel rating"
9. Check that the text after the stars is correct with and without
   your rating

Signed-off-by: Pasi Kallinen <pasi.kallinen@joensuu.fi>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>