(ipsec) add clone phase 2 option to ease duplication/modification, closes https://github.com/opnsense/core/issues/1305

PR: https://forum.opnsense.org/index.php?topic=4094

The installer user is injected for install media login, but
we authenticate against our database now instead.  This has
larger consequences that require a persistent installer user,
which is not so easy to disable/defang after installation.

Hopefully this is temporary.

(configd/templates) add "template cleanup" command, closes https://github.com/opnsense/core/issues/1238

(traffic shaper) add flush all and reload action, closes https://github.com/opnsense/core/issues/1297

Way better fix for the squid file transition.  Does not require
a manual restart anymore.

edns flag was added in 2014, but it could never be set.
Remove buffer size override along with it to further
simplify the situation.

See: https://github.com/pfsense/pfsense/commit/3b95d9e

People who use these know what they are doing, for everybody else
this is just plain confusing.

The regdhcp conditional option never really worked in the first place.
Dhcplease registration is controlled by regdhcp and regdhcpstatic
elsewhere already and we always need to include this file.

PR: https://forum.opnsense.org/index.php?topic=4041