1D Qwt Plot x-axis flips back at zoom if axis-scale was negative

[M. Gronle]

Scenario:

• Open a 2D plot
• Make a line cut from a higher to a lower coordinate (parallel to x or y) such that the 1D line plot has big x-values at the left side and smaller values at the right side
• Apply a zoom to the 1D plot (e.g. by the zoom toolbar button or by using the scroll wheel)

--> The axis is flipped back to show smaller x-axis values at the left side.

Desired behaviour: The x-axis should keep its original order (ascending or descending values)

[Robin Hahn]

itom1DQwtPlot: fixes issue #16 -> direction of pure x or y line cut stays the same also if line cut is zoomed. Remove zoom from line cut if line is moved

→ <<cset fc1f804beef9>>