This partially reverts commit 8ecaf5f9.

(proxy, remote acl's) add option to disable cert validation, closes https://github.com/opnsense/core/issues/1271

We don't need the flag anymore, it must be set through primary or
secondary console explicitly.

add validation message

(captive portal) don't try to generate invalid vouchers, closes https://github.com/opnsense/core/issues/1253

Let's keep this simple for now, just don't leave the dialog as long as the input isn't valid yet....

PR: https://forum.opnsense.org/index.php?topic=3972

PR: https://forum.opnsense.org/index.php?topic=3979.0

PR: https://github.com/opnsense/core/issues/1275

PR: https://github.com/opnsense/core/issues/1277

o Mark interface used in case of interface tracking
o Don't inject local DNS server when there is no IP

PR: https://github.com/opnsense/core/issues/1273

This doesn't really matter in the current code as it is the
default and only 'one' makes the implementation change its
scope, but for the sake of consistency let this be fixed.

We're switching to PHP 7.0 (or 7.1 maybe), php-suhosin seems dead,
and maybe someone wants to work on a newer python base.

PR: https://forum.opnsense.org/index.php?topic=3976