Changed the step for keyboard input to the minimum of x-spacing not mean anymore -- works better for d as a unit, and for the otherchoices the spacing should be constant
Bugfixing:

myWheelEvent(...)
added axes as parameter and sending it to the actual wheelevent
X-range scaling while changing units

when zommed into a graph and changing integration units, the range will now also be scaled, to be able to look at the same peaks.