Add proper per-file copyright notices/licenses and top-level license.

Add proper per-file copyright notices/licenses and top-level license.

This doesn't cover 100% of files but should clarify licensing for most Blue
Sky files.  Files written entirely by me were written while at the
Univeristy of California, San Diego and may be used under a BSD or GPLv2
license.  Some imported files may be under alternate licenses.