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 
Looks like another change got lost-- this should say "The name of the ownCloud database, which is set during installation. You should not need to change this." The installation docs go into detail on naming DBs, so we don't need to get bogged down in the details of variations in DB configuration.