Feature/seletable title more like select2

[``* `#8743` Query select menu does not work exactly like select2``](https://www.openproject.org/work_packages/8743)

Wondering if it might have been easier to have just of used select2 instead of basically re-implementing it. Never!

[Note - "...to have just of..." is a tired scottish guy trying to say "...to just have..."]
I guess this should become a separate method because it is used elsewhere too.