User-friendly free tagging

Inspired by the original fork of gr2m.

Two new options :
newText: " (new)"
freeTaggingHint: true

When using free tagging, it adds a new element at the end of the drop-down list corresponding to the new item (appended with newText).

freeTaggingHint: false disables this behavious

NOTE: I can't figure out how to filter the pull request, it only applies to commit 88d0f37