Release 0.42

Small updates for consistency:
- COPYRIGHT date
- add latest information to Changelog and NEWS

Gentoo developers suggested [tagging and releasing](https://github.com/blog/1547-release-your-software) aaphoto-0.42 in GitHub and using the downloadable archive file for packaging instead of relying on snapshots based on commit IDs. So I took another round to see if there's anything to cleanup before a release.

What do you think about releasing 0.42? Feel free to let me know if I missed something or if there are any additional steps I can help with! :)