Blender Git Commit Log

First attempt at a datatype to represent relationships (i.e. node links)

* We need a way of sharing relations between the nodes which use it. The
current design assumes that one link is shared between the two nodes
which use it. Saves mem but induces higher traversal cost?
* The relationship types enum is used to provide additional metadata about
a link, specifically, if the type of data we're interested in reside there