luci-app-ddns: Update to support ddns-scripts 2.1.0-3

- modified controller
-- remove support for ddns-scripts Version 1.x
-- ddns-scripts not correctly installed do not start
-- no config file create an empty one
- moved log settings to advanced tab
- set default syslog level "Notice"
- removed special handling for dynamic_dns_helper.sh in postinst

Signed-off-by: Christian Schoenebeck <christian.schoenebeck@gmail.com>