Cleanup and refactoring to better integrate the helicopter code into

Cleanup and refactoring to better integrate the helicopter code into
the core YASim stuff.  Mostly cosmetic: whitespace adjustment, dead
code & meaningless comment removal, a little code motion to better
partition the helicopter handling from the original code (no more
giant if() { ... } around the solver).  Added a warning to the parser
to try to eliminate the string booleans that crept in.

There should be NO behavioral changes with this checkin.