Added working rotary power engine, including a rudimentary, but
working axle and gearbox implementation. Need textures, recipes,
and some interactive features like gearboxes disengaging when
inhibited by mesecon power.
Oxygen is consumed by being underwater or suffocated by a solid
block, restored by resting and breathing. Climbing (jumping) and
swimming (or wading) tend to use stamina too, so players are
encouraged to build infrastructure, like bridges and stairs, to
avoid these penalties.
