Test switching out selectWoo for select2

[goldenapples]

selectWoo is "a fork of select2 with improved accessibility". selectWoo is also optimized for WordPress plugin development and is designed to be able to run alongside versions of select2 that other plugins may be using.

It would be good to test switching it out, to resolve some of the compatability issues that have been reported in the past trying to run select2 v4.x alongside other plugins that enqueue select2 v3.x.