[FEATURE] x,y,z entry improvements needed

[styner]

Suggestion: make the x, y, z slider bars a little bigger so they are easier to grab, and either be able to hand enter the x/y/z value on the key pad (best), or have the arrows increment by one degree (currently jumps by 10 deg). Also, if the sliders are moved from zero, currently you can’t go back to exactly zero without resetting them all.

[mlouielu]

Borrow from darktable; it can divided into 3 new improvements:

1. Double-click the label to reset the value to 0.
2. Left-clicking on the slide bar should set the value to that exact value. (The current behavior for left-clicking is to drag the slide bar, which provides a poor user experience. If the user doesn't click on the current value, they will not be able to drag it.)
3. After fixing (2), make dragging smoother.