Remaining timeline bezier curve editor features

This task groups the remaining features for the bezier curve editor:
1. Maintain the property graph expand status
2. For color properties, show the alpha channel only for custom materials
3. Allow moving keyframe points vertically on the curve (change keyframe value)
4. Limit curve segments to the space between the 2 bounding keyframes
5. Maintain and convert values when changing animation type when feasible
6. Bug: The zoom curve shortcut (Ctrl + Mouse wheel) interferes with the horizontal scroll timeline shortcut.
7. Should add a way to reset the control points to the position of the keyframe end point (ex: double clicking the end point)
8. Add curve presets?