Change copyright header on files

[rprouse]

We've discussed and agreed to shortening the copyright headers, but never came to a decision on what form to use. The console project switched to

Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt

Let's be consistent in this project and switch all files to use this.

[Dreamescaper]

Would be great to add this header to editorconfig file.