Support for input nodes: by long-pressing on a node, the app enters relationship creation mode. Selecting another nodes forms a relationship between the two. Added an inert curves layer for displaying relationship curves
WIP - render relationships in background layer
Curves now draw async.
Changed curve layer to CALayer and draw curves immediately - i.e. not with set needs display. Very quick!
Change background grid from CALayer to CAShape layer - eliminates memory warnings and crashes on iPad.