`Previous Layers` type for Layer

[ucupumar]

This type of layer will use the previous layer stacks as the input. It’s useful for adjusting the channel value in the middle of the layer stack.

• Layer type implementation
• Versioning from main channel modifiers to Previous Layer layer modifiers
• New layer option to immiadtely add modifier when creating Previous Layer layer
• Experimenting with changing the layer type to "Adjustment" layer