Bug 26439: Move cart-related strings out of js_includes.inc and into basket.js

Bug 26439: Move cart-related strings out of js_includes.inc and into basket.js

This patch moves strings defined for translation in js_includes.inc
into basket.js for translation using the new double-underscore
i81n function.

To test, apply the patch and perform a catalog search in the staff
client.

- Click the Cart link in the header menu. A pop-up should appear saying
  "Your cart is currently empty."
- On the search results page, click the "Add to cart" link next to any
  search result. The text should change to "In your cart."
- Click the "Remove" link. The text should change to "Add to cart."
- Check the box next to a title in the search results and click the "Add
  to cart" button in the search results toolbar. A message should
  appear, "1 item(s) added to your cart."
- Click the "Add to cart" button again. You should see the message "No
  item was added to your cart (already in your cart)!"
- Uncheck all check boxes on the search results page and click "Add to
  cart." You should see "No item was selected."
- Add more items to your cart so that it contains more than one item.
- Click the "Cart" link to open it.
- Click the "Empty and close" button. You should be asked to confirm,
  "Are you sure you want to empty your cart?"

TESTING TRANSLATABILITY

- Update a translation, e.g. fr-FR:

  > cd misc/translator
  > perl translate update fr-FR

- Open the corresponding .po file for JavaScript strings, e.g.
  misc/translator/po/fr-FR-messages-js.po
- Locate strings pulled from
  koha-tmpl/intranet-tmpl/prog/js/basket.js for
  translation, e.g.:

  msgid "Your cart is currently empty"
  msgstr ""

- Edit the "msgstr" string however you want (it's just for
  testing).
- Install the updated translation:

  > perl translate install fr-FR

- Switch to your newly translated language in the staff client
  and repeat the test plan above. The translated strings should
  appear.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>