Be more thorough about file copyrights

Add a copyright header to the .gitignore file with start and end
years determined from its commit history. Add copyright headers for
the current year to overrides.log and qa.log, and also add
functionality to correlate() which adds these headers from now on.
Update the copyright year on overrides.conf, which was missed in
8a37edd and later commits. All files tracked in this repository now
declare a copyright and refer to the main LICENSE file for licensing
terms.