(ipsec) add mobike switch, change leftsendcert to always. for https://github.com/opnsense/core/issues/1393

* Add priority settings to advanced firewall rule options

* fix all the previous issues with the priority rules patch and add support for the 2 prio setting

* make the advanced options auto expand, even with various priorities set to 0

Align this some more: legacy_vlan_tag() is used nowhere else,
so it's ok to change the function and clarify the text usage.

* add VLAN Priority (PCP) setting to VLAN config

* use array() instead of [] here

* add a default value for $pcp to legacy_vlan_tag()

No need to do this twice.  Added benefit of menu access to the
same functionality.

PR: https://github.com/opnsense/core/issues/1359

Fixed an issue when "Enable Transparent HTTP proxy" is on and "Enable SSL inspection" is off causes squid startup failure

PR: https://github.com/opnsense/core/pull/1388

PR: https://forum.opnsense.org/index.php?topic=4477.0

Bring back parts of f9e71141 in order to do an autoremove on
minor operations.  We still don't want the cleanup, but at
least since we have migrated to the vital flag we can be
sure that our GUI is not being purged.

move local auth functions to abstract base, add groupAllowed(). requirement for https://github.com/opnsense/core/issues/1377