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
Merge pull request #62 from morevnaproject/master

OSX and Linux compatibility fixes
Fix : [0.64.1 Dev] Convert to bones influence : crash !

Genete fix for "[0.64.1 Dev] Convert to bones influence : crash !"
Merge pull request #63 from d-j-a-y/patch-1

Fix : [0.64.1 Dev] Convert to bones influence : crash !
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
Revert workaround introduced in 6444ec06052bad0efd2f85e75b9c966bc38bdd83
Fix ValueNode_Random::clone. Still crashes later inside of Layer::connect_dynamic_param().
Change ValueNode::clone() return type - use ValueNode::Handle instead of pointer
Fix another crash related with pointers usage. Now #482 should be fixed.

See http://www.synfig.org/issues/thebuggenie/synfig/issues/482