(config) automatic recovery when config is broken, closes https://github.com/opnsense/core/issues/701

note: there's no trigger to perform the sync, so currently differences are only synced in the slipstream of otther events.
The events around synchronisation and reloading services really need some work sometime....

translation fixes

* XMLRPC: Special characters should be preserved, closes https://github.com/opnsense/core/issues/596
* XMLRPC sync only works if both systems have the same GUI port configured, closes https://github.com/opnsense/core/issues/125
* remove unreachable code

FreeBSD never implemented this.  OpenBSD did it differently and
more consequently: the `tos' tag of pf.conf(4) was properly extended
and their pf(4) can only be used to set the DSCP bit for symmetry
and general usefulness.  Until this comes back around to FreeBSD,
we'll leave it out.

translation fix for proxy page