regedit: add search feature.

regedit: add search feature.

Open up a search input with '/'. 'x' key gets the next
result.

This patch also ensures that keys are always sorted, so
that the search order matches the order the keys appear
on screen.

TODO:
	+ flesh out search interface
	+ find previous
	+ search values

Signed-off-by: Chris Davis <cd.rattan@gmail.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>