Add new parameters to Group Layer for the z_depth visibility feature
Add new members to ContextParams to include the z_depth range visibility.
When optimizing layers only add the layers that are visible in the range.
Move the new parameters description below the set hidden for outline_grow
Layer: Add member to calculate the true z depth of the layer.
Use it where applicable
Add member to retrieve the z_depth visibility (0.0 - 1.0 float range)
Fix bounding box for Paste Cavnas Layer when z depth range is enabled.
Fix hit_check and get_color to properly work
with Paste Canvases with layers with z depth range enabled.
WIP: Use recent implemented z_depth_visibility when optimizing layers
Use the transition parameter to make layers partially visible in the transition area.
Make z_depth range enabled parameter static.
Structure for new action "Layer ZDepth Range Set"
Remember the position and depth of the z_depth from the selected layers
Laeyr: Add member function to find the handle of its parent Paste Canvas Layer
or NULL if it belongs to root canvas
Merge pull request #64 from morevnaproject/random-dup-fix

Fix for #482
Consider included in visible range layers placed on right boundary too.
Default z_depth_range_depth to be 0.0
Update valuenode_step.cpp

Fix spelling of word
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.
Fix visibility of Layer_PasteCanvas.