Added dot nodes.

Added a new packed shape type for dot nodes.
Dot node drawables no longer inherit from node drawables, as they draw differently.
Dot nodes are drawn much smaller compared to regular nodes.

Factories, interaction and node graph state has been moved to nodegraph/context.

Hit testing methods having been added to the Drawable interface.
This will speed up the hit testing, and also makes the bounds and shape
accesible from comppackedshapes during unpacking.