Pistons and sticky pistons
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* These blocks are only available if digilines and/or mesecons are loaded.

Pistons push up to the setting Maximum piston nodes (default 15) in front
of the pusher when extended. Sticky piston draw back a single node in
front of the pusher when retracted. Piston also act as a digilines
conductor.

UI

Channel - digilines channel of piston.
Single move - pusher extends 1 node if checked, otherwise 2 nodes.

Mesecons
	Piston extends while power is turned on.

Digilines messages

"extend n"
	Extends the piston pusher to extent n (0, 1 or 2). If n is not given
	pusher extends to maximum extent. 0 is retracted.

"retract"
	Same as 'extend 0'.

"single"
	Sets piston to single move mode.

"double"
	Sets piston to double move mode.
