New section: project structure

[robmoss]

Discussions in recent group meetings have demonstrated a real need to outline good practices for structuring research projects, not just in terms of files and directories, but also in terms of coding practices and organisation.

This section could end by talking about the value of code clarity, and why we should treat writing code the same way that we treat writing papers and grants. Code is an important artefact for people, it's the ultimate form of explaining how your model works!