add bareos-explorer to packages
fixes problems with multiple VersionId in DB

workaround: there should be only one VersionId in the database table Version.
However, there have been cases, where it have been multiple.
This workaround prevents problems in the shell script.
changes to the database initialization

  * reduces the use of variables in database DDLs
  * move some functions for database configuration into bareos-config
  * add function to allow creation of database read-only user
  * cleanup
extract bareos-config-lib.sh from  bareos-config

with this split, bareos-config can be used as before.
Additionaly bareos-config-lib.sh can be included by other shell scripts without workarounds.
use bareos-config-lib.sh directly