[Planner Dev] Suggested images for 24x24 constraint, reset constraint and reset all constraints icons.

["lincoln phipps openmutual net" <lincoln phipps openmutual net>]

Here's what I've thought of for our missing png files for
the constraint stuff.

Providence of these images is,
Task bar from Planner, Pin I did myself using the Planner
down arrow and lightning strike from the Anjuta application.

I'll send these in a patch if people like them.

Rgds,
Lincoln.