FR: Assign Joystick Axes to Lateral Thrusters

Currently, the strafe controls/lateral thrusters can only be bound to buttons, not axes. This makes it difficult to properly utilize 6DoF HOTAS and HOSAS setups more common in newer space sims. It isn't really an issue in the vanilla campaign, but some popular modded campaigns add stronger lateral thrusters to the player ship.

If adding full axis support is too complicated (e.g. if the current lateral thrust code doesn't allow for partial thrust), there is an alternative. Some games allow binding positive/negative axis positions as button inputs. e.g. If the joystick is twisted "negatively" (let's say rightward) when binding a keypress, then the bottom half of the twist axis would be bound. If the same joystick were twister "positively" (leftward in this example), then the upper half of the twist axis would be bound.