Bug 34085: Remove the use of event attributes from basket groups template

Bug 34085: Remove the use of event attributes from basket groups template

This patch removes the use of event attributes (onclick, onsubmit) from
the basket groups template. These events are defined now along with the
other in-page JS.

This change allows us to move the scripts to the bottom of the page.

Unrelated changes: There was no confirmation tied to the process of
deleting a basket group. I've added one. And there were several "MSG_"
variables defined which were unused and have been removed.

To test you should have at least one vendor with at least one basket
group.

- Apply the patch and go to Acquisitions.
- Locate a vendor with an associated basket group.
- Edit a basketgroup
  - Confirm that editing works correctly (leaving "Close basket group"
    unchecked")
  - Confirm that editing works correctly with "Close basket group"
    checked.
- In the list of closed basket groups, confirm that all the controls
  work correctly.
- Create an empty basket group and confirm that clicking the associated
  "Delete" button in the list of basket groups triggers a confirmation,
  "Are you sure you want to delete this basket group?" Test that both
  confirming and cancelling work correctly.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>