[development] better autocompletion?

[Moshe Weitzman]

killes: I got it. Requires no forms changes at all.

First, some boards call this operation 'prune' and 'graft'. Prune is
removing a comment branch and graft is attaching it elsewhere. This borrows
from plants the language of gardening plants.

You add three links to comment_mover_links(). First, you add a link called
'prune' on every comment for priveleged people. When admin clicks that, all
'prune' disappear and in their place two new links: 'graft' and 'cancel
prune'. When user clicks a graft link, you now have source and target and
can move accordingly. 'cancel' just sets it so that the 'prune' links show
up again.

If you don't like this language, you could use other. I like its organicness
:)