In order to allow users enter tags quickly and steer them towards using official tags, we need a widget which extends the inline edit box with the ability to suggest official tags from a pre-defined list.
The additional required behaviour is:
* As the user types the last word is searched within all the official tags.
* If there are any tags containing the word, a list opens below the textbox, alligned to the left of the current word.
* The list contains all matching tags and is updated as more characters are entered.
* It is possible to navigate the list with the down/up arrow keys.
* Clicking tab completes the word in the text box to the currently selected item from the list (and inserts a space).
* Clicking tab again immediately cycles through the tags in the last list.
* Clicking enter also completes the word (and inserts a space) but the last list is forgotten.
Māris, assigning to you, since you started working on this, but shout if you need me to take some of the work.