Drag direction of levers

[gilbertohasnofb]

When I inverted the scrolling direction of the throttle and mixture levers, I also ended up inverting the click and dragging direction as well (which is very anti intuitive). The c172p shows that it's possible to have the proper scrolling direction together with the proper clicking and dragging direction, so I will study how to implement this and make a PR to fix it as soon as possible.

[gilbertohasnofb]

Okay, so what's needed is to add this to the c150-set.xml file:

        <!-- Fix scrolling direction of knobs -->
        <mouse>
            <invert-mouse-wheel type="bool">true</invert-mouse-wheel>
        </mouse>

Then inverting the value of all <factor> in all slider animations.

[gilbertohasnofb]

@Harald67 this is done, but before I create a new PR for this fix we have to merge this other PR #22 so I can update the xml files that are altered in both branches. Would you mind taking a look at that standing PR in the link above? We just need to fix that issue you are having with the FOV