various fixes to ament-copyright and add --allowed-licenses argument

[alsora]

Signed-off-by: Alberto Soragna [email protected]

This PR addresses the bugs mentioned in #414.
This PR adds the feature described in #415

[superdyoll]

What's stopping this branch from being merged? Just re-discovered this bug myself and it'd be nice if this bug was fixed. It's hidden in the released version of ament_copyright due to the typo in add_copyright_year in main.py of the missing s in copyright_identifiers that this merge request fixes. Would prefer that ament_copyright updates the copyright year itself rather than having to write a separate script to do it.

Edit: Looks like @clalancette is the one who's managing this repo these days, so tagging them here to hopefully bump this up the agenda as I imagine I'm not the only one hitting this issue as we enter the new year.

[clalancette]

I think this PR does a little too much, in my opinion. To get this in, I think 3 PRs would help:

1. Adds in --allowed-licenses, along with the changes to support that feature.
2. A bugfix for the "copyright_identifiers" bug (this will be easy to backport)
3. The fixes to change to a regex for the copyright information

Split up that way, I think we could get this in.

[superdyoll]

@clalancette have raised a new PR here #466 to fix the bug in --add-copyright-year caused by the lack of s on identifiers. Unfortunately it wasn't as simple as just typing s as the code had to be updated to work with multiple copyright notices at the same time.