Peter M. Groen / FlashMQ

This also contains some fixes/unifications for traditional
authentication, error handling specifically.

And one line about correlation data that was a bug.

This saves some allocations.

This also meant having to set the C++ standard to 2014.

The getCopy() methods of sessions and mqttpackets can't be changed,
because of access errors (private).

This avoids changing which thread runs the code.

Also let auth_plugin_serialize_init affect cleanup serialization.

Encrypted version only.

This fixes the 100ms wait time requirement.

This allows creation of multiple listeners, with different protocols
and/or SSL certificates.

Related change: settings is now a class that is copyable and assignable,
and is done so to each thread on reload.

Semi-related fix: fix crash in quit when multiple threads initiated it.
This came to light when testing the auth plugin settings.

It can be defined in the config file, along with options.

I kind of need a config file parser first, so I'm going to make that.