(legacy) add x509_extensions selection to cert_created, related to https://github.com/opnsense/core/issues/81

(legacy) remoev duplicate cert code from usermanager (use redirect instead), closes https://github.com/opnsense/core/issues/59

Additional fields in MVC library

This module was used in the old XMLRPC client code, but is no longer
needed.  Removal was escalated by FreeBSD when the oniguruma4 dependency
of the php56-mbstring module was marked BROKEN.

We're moving PPTP back, the whole discussion is rather pointless
to be honest.  We'll make it a plugin for 16.7, I think that's
only fair for users who know what they are doing.

minor typo

Signed-off-by: Isaac (.ike) Levy <ike@blackskyresearch.net>