Feature request: Adding "per container" logging into the container creation logic, other support for syslog

[vielmetti]

Support unified logfile management in container creation by allowing a logging destination to be set for each and all containers.

A goal is to obviate the need for a separate logfile and syslog management container, and to enable Portainer to have a more robust debugging capability when things go wrong.

As discussed on gitter here: https://gitter.im/portainer/Lobby?at=58662614af6b364a290fd290