metomi/rose#486: tutorial
metomi/rose#486: tidy
metomi/rose#486: manually tidy index
metomi/rose#486: feedback following review
metomi/rose#486: fix info
metomi/rose#486: better phrasing
Merge pull request #523 from benfitzpatrick/486.opt-conf-tut

#486 - optional configuration tutorial
metomi/rose#508: update