Refactor muscle based engine code.
Removed PEDAL and HAND_RIM flags. All checks on these are replaced with
checking the fuel type is muscle.
Replaced method call with equivalent variable.
Remove PADDLES flag from boat mod.
Puts most frequent access with muscle engines into a variable instead of
calling the method often.
Added comments. Moved around engine failure message.
Simplified velocity add logic. Same with actions on thrusting.
Made music play even if velocity not changed or something bad happened.
Limited muscle vehicles mass move to player strength. Added some
comments.
Relaxed motor checks on install.
Relax muscle regular engine mount limits.
Allow alternators installable to muscle engines.
Added electric bike.
Fixed brackets. Alternators now charge on pedals.
Removed variable, replaced with original function call to prevent stale
value bugs.
Fixed bicycle having default sound level. Changed meaning of engine_on
to say that at least one engine of any type, including muscle, is on.
Reduce difficulty of installing a muscle engine.
remove redundant parameter
Fixes load always being either 0.1 or 1.0. Aborts thrusting if load <
0.1. Torsion ratchet power gen dependent on load, 1pow with 1load,1turn,
or 0.5load,2turn or 0.1load,10turn etc.
Added hunger and fatigue cost to muscle engines.