Try and switch to commit status for CodeCov (#1166)

* Try and switch to commit status for CodeCov

Try and switch to commit status rather than comments for CodeCov

* Add some specific status entries

* More testing

* Run with comments as well for now, until we've worked out if we've sorted it

* Simplify what we actually need to change from the default

Pending decisions on how many separate project bits we want returned.