Uses Aplpy FITSFigure in Npred plots

Still a few things to do here (I haven't figured out how to do these yet).
- [ ] Add colourbars to the plots
- [ ] Use better colour scale for the background ratio image
- [ ] Add titles to each of the subplots
Anything else?
I don't really know why this has changed... maybe some other bug was fixed in the changes you made recently (the results look slightly better)