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