[Bf-codereview] Node Group Interface (issue 5593050)

[lukas.toenne at googlemail.com]

Reviewers: bf-codereview_blender.org,

Description:
This patch implements one of the main features described in my recent
code.blender.org blogpost [1]

It replaces the current lists of sockets on either side of the group
editing window by internal "proxy nodes". This is avoids long node
connections from the sides of a node group and provides a place to edit
all the details of a node group interface socket. It also simplifies
code by removing the need to take additional socket lists into account.
In the future the proxy nodes could be used for creating external
interfaces for regular (non-group) node trees as well.

User wiki documentation can be found here [2]. (I noticed there is
currently no wiki docs section on general node editing features, beside
specifics for shader/compositor nodes. Would be a good idea to make one
and integrate this info there.)

NOTE: This version of the patch does not include changes to
startup.blend for size reasons, which means the proxy node theme color
will be black by default.

[1]
http://code.blender.org/index.php/2012/01/improving-node-group-interface-editing/

[2]
http://wiki.blender.org/index.php/User:Phonybone/NodeTreeInterface

Please review this at http://codereview.appspot.com/5593050/

Affected files:
   intern/cycles/blender/blender_shader.cpp
   intern/cycles/render/nodes.cpp
   intern/cycles/render/nodes.h
   source/blender/blenkernel/BKE_blender.h
   source/blender/blenkernel/BKE_node.h
   source/blender/blenkernel/intern/node.c
   source/blender/blenloader/intern/readfile.c
   source/blender/blenloader/intern/writefile.c
   source/blender/editors/include/UI_resources.h
   source/blender/editors/interface/resources.c
   source/blender/editors/space_node/drawnode.c
   source/blender/editors/space_node/node_draw.c
   source/blender/editors/space_node/node_edit.c
   source/blender/editors/space_node/node_intern.h
   source/blender/editors/space_node/node_ops.c
   source/blender/editors/space_node/node_select.c
   source/blender/editors/space_node/node_templates.c
   source/blender/makesdna/DNA_node_types.h
   source/blender/makesrna/RNA_access.h
   source/blender/makesrna/intern/CMakeLists.txt
   source/blender/makesrna/intern/rna_nodetree.c
   source/blender/makesrna/intern/rna_userdef.c
   source/blender/nodes/CMakeLists.txt
   source/blender/nodes/NOD_common.h
   source/blender/nodes/NOD_socket.h
   source/blender/nodes/composite/nodes/node_composite_common.c
   source/blender/nodes/composite/nodes/node_composite_moviedistortion.c
   source/blender/nodes/intern/node_common.c
   source/blender/nodes/intern/node_common.h
   source/blender/nodes/intern/node_exec.c
   source/blender/nodes/intern/node_socket.c
   source/blender/nodes/intern/node_util.c
   source/blender/nodes/intern/node_util.h
   source/blender/nodes/shader/nodes/node_shader_common.c
   source/blender/nodes/texture/nodes/node_texture_common.c
   source/blender/nodes/texture/nodes/node_texture_output.c