Merge Nodes Efficiency Tools with Greg Zaal's Node Wrangler

New Features:
- Lazy Connect
- Lazy Mix
- Delete Unused Nodes
- Swap Outputs
- Reset Backdrop
- Add UV Layout attribute node
- Add Vertex Color attribute node
- Shader Viewer
- Frame Selected Nodes (wrap nodes in frame)
- Reload all images
- Modify Labels

Modified features:
- Switch Node Type - now every node's type can be changed to any other.
Links will be preserved whenever possible.

All old and new features documented on wiki page:
http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Nodes/Nodes_
Efficiency_Tools