restructure startup of dnymaic_dns_updater.sh
 - first run load_all_config_options (it returns 1 if SECTION_ID not found) #779
 - set all defaults if necessary
 - verify if username and/or password is needed inside update_url #779
 - remove wait - will be done by retry_interval and retry_count if communication fails
provider specific update scripts
 - verify if username/password are needed
services_ipv6
 - added freedns.afraid.org
 - IPv6 should work due to their documentation
minor fixes

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