Possibility to exclude own dependencies in download-licenses goal

[Matze2]

Our own artifacts do not have any license information which leads to false warnings like
[WARNING] POM for dependency : has an invalid license URL: null
[WARNING] No license information available for: :

While this is only a cosmetic issue it might happen that real warnings about missing license of foreign components get overseen.

It would be nice to have some exclude possibilities similar to add-third-party.
For us having <excludedGroups> and <excludedLicenses> (if this is possible) would help a lot.

Thank you very much that development continues for this useful plugin!

[Matze2]

I gave it a quick try and added an "excludedGroups" property in AbstractDownloadLicensesMojo class and adjusted the getter and it immediately worked that we could exclude our own groups by regexp pattern for download-licenses goal.
So the existing code is already 99% prepared for that.

[tchemit]

@Matze2 Ok I have just implements for (include/exclude) for scopes, groupIds and artifactIds.

Have a look to it ISSUE-40 for configuration.