interact directly with machine blocks when marks displayed
hold sneak and punch a block to abort interactive setup
allow removing keypad password
add place sounds for mover in normal, dig and transport modes
somewhat rework player punch in space
code maintenance
can_dig; fix player - optional
luacheckrc: remove unused_args = false
ball: balls bounce on liquids, glow with energy, can push objects, remove balls with incorrect position
space: push players harmlessly