add AUTHORS and COPYING files

The AUTHORS file contain the people that appear in the copyright
headers plus myself.

The COPYING file contains the AGPLv3 which is the selected
license according to discussion with Harald.
diff --git a/AUTHORS b/AUTHORS
new file mode 100644
index 0000000..10719cf
--- /dev/null
+++ b/AUTHORS
@@ -0,0 +1,3 @@
+Harald Welte <laforge@gnumonks.org>
+Holger Hans Peter Freyther <zecke@selfish.org>
+Pablo Neira Ayuso <pablo@gnumonks.org>