Drop dependency to Plexus utils - rewrite logic for DirectoryScanner

[slachiewicz]

New feature, improvement proposal

We use only a small part of plexus-utils related to DirectoryScanner would be good to try to rewrite it with native Path instead of String operations

[desruisseaux]

Done here. Will submit a pull request after other pending pull requests such as #240 and #234 have been merged.

[desruisseaux]

Replaced by pull request #242.