COPYING: Add licensing information. This supersedes script licensing

except for trigger.pl, cron.pl, and usercount.pl.

COPYING

+All scripts, other than trigger.pl, cron.pl, and usercount.pl are released
+under the following terms, even if specified otherwise:
+
+Copyright (c) 2012 Kiyoshi Aman.
+
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+This software is provided 'as is' and without any warranty, express or
+implied.  In no event shall the authors be liable for any damages arising
+from the use of this software.
+
+trigger.pl and usercount.pl are both released under the GNU GPLv2.
+
+No license information is available for cron.pl; it is presumed to public
+domain. If you were involved in writing cron.pl, please let me know.