Uses Aplpy FITSFigure in Npred plots

Still a few things to do here (I haven't figured out how to do these yet).
- [x] Add colourbars to the plots
- [x] Use better colour scale for the background ratio image
- [x] Add titles to each of the subplots

Anything else?
Changing to mirror in convolution increased this to 282, although the mean is closer to 1 on the ratio image with 'mirror'.