Various fixes to make Layer ZDepth Range Set work.
Action is not candidate if layers are in root canvas.
Calculate properly z_depth_range_depth value to set.
Action is ready if there isn't new calculated z_depth position.
Add actions to change the Layer PasteCanvas parameters.
Add some warnings to explain why the paste canvas is not found.
Make the action not ready for exported canvases
Z Depth visible layers are shown with bold letters in the layer panel.