Add animation hooks into cf-plot

[bnlawrence]

xconv2 needs some things to happen to enable animation frames to work without writing files. Details anon,

[sadielbartholomew]

I am moving this back to 'Backlog' because I don't think we should consider work 'done' until it is merged and the corresponding PR is still in review (I've yet to carve out time to review it).