Move control lever input gain to IC-safe file

[EnzoF98]

Posting in general WW2 wishlist, as it affects most (if not all) warbirds.

Controlling levers such as the prop speed lever with digital buttons is far too sensitive for precise control over your engine settings.

Lowering the "gain" parameter as described here works really well: 

 

However, this fails the integrity check and gets overwritten with every update. 

It would be great to have this available in a file that is safe from the integrity check, or perhaps as a slider in Special Options.