clearified description for bareos-database-common

Closes: #768606 (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=768606)
Thanks: Davide Prina
on purge, also remove /etc/bareos/.rndpwd

Closes: #769096 (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=769096)
Thanks: Andreas Beckmann
get rid of circular dependencies

Remove circular dependency between bareos-database-common, bareos-database-mysql, bareos-database-postgresql and bareos-database-sqlite3.

Closes: #769536 (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=769536)
Thanks: Bill Allombert
changelog for 14.2.1+20141017gitc6c5b56-4

Thanks to Joerg for preparing this release!