Bug 33868: Upgrade the Multiple Select plugin in the staff interface

Bug 33868: Upgrade the Multiple Select plugin in the staff interface

This patch upgrades the Multiple Select plugin in the staff interface
and adds some minor adjustments to system preferences CSS to accommodate
the change. The listing on the about page is updated with current
information.

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

- Go to Administration -> System preferences.
- Test some preferences which use the plugin, e.g.
  - ApplyFrameworkDefaults
  - CoceProviders
  - OpacHiddenItemsExceptions
  - OPACAllowUserToChangeBranch
- Confirm that the menus look correct and work correctly.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>