Bug 16477 - Improve staff client cart JavaScript and template

Bug 16477 - Improve staff client cart JavaScript and template

This patch makes several changes to the cart JavaScript and template. In
the template:

- Remove "onclick" attributes in favor of defining events in the
  JavaScript.
- Add a [% BLOCK %] section for some repeated markup.
- Add some Font Awesome icons (I didn't add icons to all controls
  because I thought it looked cluttered).
- Move the batch modification control out of the toolbar and into the
  group of controls which affects selected records. I think this is a
  logical grouping, and makes more sense than having a drop-down menu in
  the toolbar with a single menu item.

JavaScript:

- Created separate "cart.js" file so that JS could be moved out of the
  template without loading up basket.js with event functions which are
  not needed on every page in the staff client.
- Fix JSHint errors.

To test, apply the patch and clear your browser cache if necessary.

- Add multiple items to the cart in the staff client and open the cart.
- Confirm correct functionality of these toolbar buttons:
  - "More details" (and the corresponding "Show less")
  - "Send"
  - "Print"
  - "Empty and close"
- Confirm the correct functionality of all the selection controls:
  Select all, clear all, Remove, Add to a list, Place hold, Batch
  modify, and Batch delete.
- Confirm that clicking any title in the cart opens the correct detail
  page in the parent window.

Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
https://bugs.koha-community.org/show_bug.cgi?id=1647

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>