Organize output (warnings, coverage) into sections per filename

[Andreas Abel]

Looking at the output of haddock to the user,

  ...
  50% (  1 /  2) in 'Test.Tasty.Silver.Interactive.Run'
  Missing documentation for:
    Module header
Warning: 'goldenTest1' is out of scope.
    If you qualify the identifier, haddock can try to link it anyway.
  66% ( 12 / 18) in 'Test.Tasty.Silver.Internal'
  ...

I am a bit confused which file the warning belongs to.

Suggestion: organize the output better so that it is always clear which file is talked about. E.g. description list or bullet list where filename comes first.

E.g.:

- Test.Tasty.Silver.Filter
  71% (  5 /  7) coverage
  Missing documentation for:
    filterWithRegex (Test/Tasty/Silver/Filter.hs:90)
    RegexFilter (Test/Tasty/Silver/Filter.hs:46)

- Test.Tasty.Silver.Interactive.Run
  50% (  1 /  2) coverage
  Missing documentation for:
    Module header

- Test.Tasty.Silver.Internal
  Warning: 'goldenTest1' is out of scope.
    If you qualify the identifier, haddock can try to link it anyway.
  66% ( 12 / 18) coverage
  Missing documentation for:
    Module header
    GoldenResult (Test/Tasty/Silver/Internal.hs:92)
...