Increase Chinook landing speed and removed turn before landing.

Fixes #5054, Allows for any helicopter to choose to turn to the initial facing before landing, and sets the default to disable the turn since this only affects the chinook.  I kept the previous functionality as a property because I thought it might make sense for single player for visual effect (Allies01) or for some other mod.

Increases the chinook's ascend/descend speed for faster landing as well.

Also documents some of the helicopter trait properties, since you can never have too much documentation.