Tagging: Add support for filtering project TPs using tags

Fixes bug 3037
Tagging: Use Select2 in tag filtering UI

Fixes bug 3038
Tagging: Use AJAX for filtering TPs in project overview

Fixes bug 3070
Tagging: Don't reload the whole page when adding a tag to a TP in Project overview

Fixes bug 3075
Tagging: Don't reload the whole page when adding a tag in TP overview

Fixes bug 3074