REF: split pixel-array effects into RasterEffect (bad name) and ChaseEffect (animated scrolling)
ENH: finish the scrolling test pattern generator
ENH: plumbing for OPC addresses, round 1/n
LNT: purge debugging logs
ENH: wait a few seconds then try again if the opc server goes down on a socketerror. ENH: broadcast opc pixels in opc address order, not patch sheet order.