Updated copyright years for all files under our license

This PR modifies essentially every file in the repo to update the years of copyright, which should match any year there has been a release: 2014-2019.

I also added a utility to automatically update the copyright statements, and documented that this should be run for each release, it should have no impact when run for a year that is already included in the copyright.

@alurban, @areeda, @scottcoughlin2014, you are listed as copyright holders for one or more files, so I need explicit approval from each of you.