Simplify copyright statement

[HalosGhost]

In the initial release, only two parties needed to be named for copyright. That's no longer the case due to several open-source contributors (thank you and welcome)!

Rather than have the copyright notice need to be updated across all the files which contain the notice, we should simplify this process to maintain a single list:

• Create an AUTHORS file
• Migrate all known copyright holders to AUTHORS
• Update all copyright notices to point to the AUTHORS file
• Explore automation / update process to ask people to include their name in AUTHORS if they wish to have their copyright recorded