Order message by filename

[Ruudieboy]

Messages are not sorted by filename. It would useful if they are sorted by (filename, rownumber). This way it's easier to fix multiple issues in a single file.

Current output:

Unused imported variable `spinner` in file "src/main/elm/Views/MaatschappijRow.elm" at ((7,103),(7,110))
Unused imported variable `type_` in file "src/main/elm/Views/Forms/Softwareleverancier.elm" at ((7,108),(7,113))
Unused imported variable `value` in file "src/main/elm/Views/Forms/Softwareleverancier.elm" at ((7,115),(7,120))
Unused imported variable `a` in file "src/main/elm/Views/Maatschappijen.elm" at ((8,27),(8,28))
Unused imported variable `on` in file "src/main/elm/Views/ZaakStoppen.elm" at ((8,28),(8,30))
Unused imported variable `form` in file "src/main/elm/Views/Dialogs/Maatschappij.elm" at ((8,32),(8,36))
Unused imported variable `onClick` in file "src/main/elm/Views/ZaakStoppen.elm" at ((8,32),(8,39))
Unused imported variable `i` in file "src/main/elm/Views/Maatschappijen.elm" at ((8,39),(8,40))
Unused imported variable `Save` in file "src/main/elm/Views/SoftwareleverancierRow.elm" at ((8,40),(8,44))
Unused imported variable `i` in file "src/main/elm/Views/Dialogs/Maatschappij.elm" at ((8,42),(8,43))
Unused imported variable `span` in file "src/main/elm/Views/Maatschappijen.elm" at ((8,42),(8,46))
Unused imported variable `label` in file "src/main/elm/Views/Dialogs/Maatschappij.elm" at ((8,45),(8,50))

In the output above there are 3 issues in src/main/elm/Views/Dialogs/Maatschappij.elm but they are scattered in the output.

[stil4m]

Fix will be shipped in the next release.