Documentation character assassination

[DavidT3]

First step to improving the documentation is going to be to just read through all of it, and be really critical of what is in it, how it is laid out, and how I presented things.

This is not an incredibly urgent project, so we can do this piecemeal over time - I think maybe a separate notes project entry for each section will be the way to go, so everyone can collate their notes about a particular bit in one place.

The two main things we want to achieve with this (I think, please everyone say if they think there is something else critical we need to improve about the docs) is that the way I wrote the tutorials (for instance) focuses too much on the details of how things are working, which most users don't want or need to know; and the other thing is that the generalised tutorials should be supplemented by very targeted 'case studies' like we have in DAXA docs (these would help someone achieve a specific scientific goal, like say measuring R500s for a sample of clusters).