Config update

Copy fixes from owncloud/documentation#594 and apply them onto config.sample.php

@carlaschroder Have a look at a96f7c1 I added some fixes. Are you fine with them?

cc @PVince81 @wakeup @DeepDiver1975 @LukasReschke 
No this is in core https://github.com/owncloud/core/blob/6323d5fb3aa26ca777004595db255074e2f31079/lib/private/templatelayout.php#L33:L41 and shows a notification about the new ownCloud version.