Add control option that displays sub menu listing all installed engines
Added message about engine that has been toggled
added enabled flag to all individual vehicle parts
added empty methods for later
Fix bug when no engine selected.
Now toggles the engine enabled flag for the part
added engine status to engine select menu
added checks to velocity, fuel usage, etc to update for disabled engines
fixed fuel usage calc
loops through engine select menu until cancel is selected
Changed cancel to finish
if new engine config has a safe velocity less than current velocity,
reduce cruise velocity
Added save load of part enabled boolean
fixed comment
moved engine control choice to seperate method
Alternator disabled when attached engine not running.
Prevented engine control if less than two engines
Fixed engine counter
Fix std::round()
Refactored code
Renamed p variable to e where appropriate, changed type to size_t where
was int.