ImageEffect Animation 2.0

[Variable-ind]

2nd iteration of #836 (also fixed 2 bugs in previous iteration)
moved the animation system to it's own separate AnimatePanel.tscn

Added:

• It is now possible to preview other frames as well, not just the current frame

Changed:

• Made the animate system more intuitive
• Property animation now uses SceneTreeTween instead of Lerp which allows us to set:
  • Transition type and Ease mode
• Animation starts from left of timeline and ends at right (in old system animation just went through whatever order cels were placed in selected cel array)

Fixed:

• [0.11.0 and earlier issue] fixed issue when changing affect mode to something else and the back to Selected cels made the animate system appear even if no animatable properties were set for that image effect
• [0.11.0 and earlier issue] fixed value and saturation sliders being divided by 360 (when they should be divided by 100). this bug was introduced in Animate image effect properties #836 (sorry about that)

Visuals:

here's animating an outline from 10 to 20 in old system

test-.6.mp4

here's doing the same thing in the new system

test-.7.mp4

[OverloadedOrama]

This is amazing, excellent work. Thank you!