pfSense

Disable state killing on gateway failure by default for new configs.
Clarify the text describing the option while here.

Fixes #2979

. Change max value for traffic and packets graphs to 20GigE
. Bump config version to 9.6
. Write a config upgrade function to tune current rrd files to the new
max value

After some discussions it is better to make this a tunable and allow its value change from administrator.

Fix IPv6 Prefix ID default value

. Always initialize it to 0 when it's undefined
. Remove unecessary initializations and checks
. Bump config version to 9.5
. Write an upgrade config function to initialize old configs properly

Upgrade code & config default version

Update config default with powerd battery mode

Adjust RRD captive portal graphs for CP zones

- Create RRD configs per zone
- Add tabs to see graphs per zone
- Migrate existing rrd files to default cpZone
- While I'm here, call unset() for $rrdcreate and $rrdupdatesh

Resolves #2655

Make sure default config complies with latest version

Update the default config.xml to 9.2 so it does not trigger config.xml upgrade during install of a new system

Add IPv6 privacy settings tunables. Keep the default FreeBSD value for them, that is disabled. This implements feature request #2587