Bug 34509: Use select2 to load vendors on basket creation

Bug 34509: Use select2 to load vendors on basket creation

This patch moves the dropdown to use select2 and avoids loading all
vendors at page load.

To test:
 1 - Create some extra vendors in your system, ideally over 20
 2 - Search for a vendor in acquisitions
 3 - Click 'New->basket'
 4 - Note the dropdown of all vendors
 5 - Choose a vendor and create a basket
 6 - Apply patch
 7 - Repeat
 8 - Note only a partial list of vendors is loaded
 9 - Search in the dropdown and confirm vendors are returned
10 - Select a vendor and create the basket

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>