#29 Tag autocompletion

[Tim De Pauw]

When supported, tags should be autocompleted through
AJAX. The way I see this:

- Suppose the user has already entered a number of
tags, separated by spaces
- He starts typing a new tag
- An AJAX-based search retrieves the existing tags that
start with the characters the user has entered
(actually, just the first result?)
- When the search completes, the system checks if the
found tag still matches
- If it still matches, the rest of the tag is
automatically appended, and selected
- Two options:
-- If the user presses enter, absorb that event, keep
the tag, add a space, and place the caret after that space
-- If the user continues to type, check if the tag
still matches
--- If it matches, shorten the selected range so only
the suggested part is still selected
--- If it doesn't match, remove the selected part and
search for new matches

Implementing this as a cross-browser feature is going
to be fun.