nodogsplash2: change configuration defaults (#341)

nodogsplash2: change configuration defaults (#341)

nodogsplash2: change configuration defaults

Changes:
* set default to NoDogsplash enabled as rest of config should now be safe and is possible to SSH to router to stop NDS if needed
* change clientidletimeout to 120 minutes (2 hours)
* add clientforcetimeout set to 1440 minutes (24 hours)
* comment out the two provided example authenticated_users block lines
* add list authenticated_users 'allow all'
* comment original list authenticated_users allow... entries and leave them as examples
* set preauth default to no use remote DNS. All devices used at a public wifi venues should be configured for DHCP. To force the use of the local DNS server makes DNS tunnelling very inefficient if not unusable on a typical OpenWrt device.
* set fw_mark settings for compatibility with other OpenWrt packages