Update the 2018 copyright in all files

(IANAL) As far I as understand the US copyright law, there's no real reason why to update the copyright to new year only when you touch the file.

Instead of cluttering the git history with two extra commits for almost every merge request, the source files should be updated in bulk and add 2018 everywhere.

A reminder to do the same thing on 1. January next year should be set in the cron job to be sent to bind team list in addition to the merge requests on maintained branches.