Add title to plots about fsbrain

[dfsp-spirit]

Currently not. and it would involve some fiddling. Because the renderer we use leaves too much whitespace between the individual tiles of a multi - figure plot (the different view angles of the brain), I do some magic with image magick (basically cut stuff apart, remove whitespace borders, merge again) to produce the final image.

As a result, the final product is not not something I can easily plot on. It can be done of course, but it involves guessing the required space for the title, expanding the image at the top, and computing exactly where to put it then. I have done that for the figure captions already, and it was not really much fun and still has its limitations. So I think it's better to put the title in some other way or abuse the caption for it.