hello docs on the most important thing for most users coming to a new project: you use `mdm update`, and it goes to space.
getting started page.  mostly, a set of quick pointers to other sections of interest.
oh dear, there are more places where i've got the hardcoded release numbers in example urls now.  update.
really hammer home that `mdm update` is the thing to do when wanting a clean and correct workspace.
more topics that should be covered in link discussion
lots of concrete examples of what git-status looks like and what it can tell you.  also describe how mdm-update behaves in response to various dirty working tree situations.
fill out a list of links to subsections for docs chapters that don't have their own leading content yet.
Merge branch 'doc'