Improve version output of the witness linter

[MartinSpiessl]

This really has to different aspects that could be improved:

1.: currently the linter does not output its version when it is run. In practice, it is a slight advantage to have some version clue in stdout, so we might want to simple add such a print statement, which should not be that hard to add.

2.Currently we manually bump the version. Ideally the version is determined automatically from the git history (git describe --dirty from the last tag in the repo). That way we always have a commit-precise way of knowing which version was actually executed.