Issue 570 lever adjustments for small changes

[hbeni]

• Add friction lock / vernier feature
• Ammend travel of prop lever

Fix #570

[hbeni]

@TheFGFSEagle If you don't mind; would you verify this?

I think its ready and good as it is now.

[hbeni]

(Edit: Now this is also in-sync with the c172p: https://github.com/c172p-team/c172p/pull/1498)

[TheFGFSEagle]

Will test later this day ! :)