add unsubscribe script

tools/unsubscribe

+#!/bin/bash
+# unsubscribe - removes an address from a list
+# NOTE: this script requires the current user has read access to the db
+
+echo "removing $1 from $2:"
+
+# remove all list subscriptions
+mysql --batch --database=sympa --execute "delete from subscriber_table where use
+r_subscriber='${1}' AND list_subscriber='${2}'"