Changed COPYING to MarkDown format, added a link to the FSO's Licensing page at wiki in github

Author: Kiloku

COPYING COPYING.mdCOPYING renamed to COPYING.md

@@ -1,14 +1,15 @@
 Volition Copyright (applies to original FreeSpace2 source code
 developed and released by Volition):
 
-"Copyright (C) Volition, Inc. 1999.  All rights reserved.
+>Copyright (C) Volition, Inc. 1999.  All rights reserved.
 
-All source code herein is the property of Volition, Inc. You may not
+>All source code herein is the property of Volition, Inc. You may not
 sell or otherwise commercially exploit the source or things you
-created based on the source."
+created based on the source.
 
 
 Modifications by members of the FreeSpace Source Code Project are
 released under whatever terms the individual authors choose, but the
 above notice continues to apply to all fs2_open code.
 
+See [**Licensing**](https://github.com/scp-fs2open/fs2open.github.com/wiki/Licensing) for more information.