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- Added "Node Group" utility node
- Added "Group Nodes" and "Edit Group" operators to create/modify node groups
- Added new keymaps for creating and editing node groups (Ctrl+G, Tab)

- Added UI panel base class and 3 new panels: "Properties", "Utilities" and "Node Groups"

- Added "Send to Sverchok" utility node to pass mesh data (verts/edges/faces) to Sverchok node (Requires "Receive From Sorcar" node in Sverchok nodetree)
- Added "Receive from Sverchok" input node to fetch mesh data (verts/edges/faces) from Sverchok node (Requires "Send To Sorcar" node in Sverchok nodetree)

- Added "Text Block" constant node to output multi-line string from Text Editor

- Added node interface base class and sub-classes for all sockets to support node-groups (with custom properties)
- Added Wiki and Bug Reporter links in add-ons manager

- Improved object input nodes to clean up geometry when removed
- Improved socket base class to show error icon when execution fails
- Improved "Custom Object" input node: inherit from input base class, apply all modifiers before execution
- Improved Import/Export nodes to select directory path using file picker UI
- Improved "Material Parameter" node to show all available nodes & sockets as a drop-down (search)
- Improved "Scene Info" node: added new outputs for world unit scale length, active/selected/all objects from the scene; removed "Realtime" tree property

- Improved "Duplicate Object" node: added "Linked" input socket
- Improved "get_override" and "sc_poll_op" helper methods
- Improved all operators: show tooltips, new category (prefix)
- Improved all socket base classes to support node-groups

- Fixed socket base class to avoid executing node-group input nodes
- Fixed "Dissolve" node
- Fixed nodetree execution
- Fixed "Array" socket label (length of the evaluated array)
- Fixed "Instancing" node