Make verbosity a variable rather than binary quantity.

We can now selectively increase the amount of information printed out.
Colour warning/failed status if writing to a terminal.

Want problems to stand out was much as possible!
Include test and benchmark values in error/warning line.
More pedantic formatting.
Order tests by their paths.

This is slightly more pleasing than having a random ordering.  Hopefully
it won't be a feature people come to rely on!