#7 Refactor graph rotation behaviour implementation

[Brendan Cleary]

Currently all graphs are affected by the behaviours
defined in the scene graph defined by the visualisation
environment, some of these behaviours such as rotation
conflict with other graph layouts such as force
directed. We should move graph specific interaction
behaviours (such as rotation) out of the visualisation
environments scene graph and into the scene graph
generated by the graph layout algorithms that are
specific to those graphs. This would then allow
different graph types to be attached to the
visualisation environment without having to worry about
behaviour dependencies.