Fix for the custom_nodes.py template. Socket classes now return their drawing color in a callback instead of a simple property, this makes it possible to change a socket color e.g. based on data type.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55507 954f8c5b-7b00-dc11-b283-0030488c597c