dird: add command line feature to print specific resources

[joergsteffens]

The bareos-dir prints its configuration when called with the -xc parameter.
This change allows to print only specific resources:

print full configuration

bareos-dir -xc

print all Job resources

baroes-dir -xcJob

print the Job resource BackupCatalog

bareos-dir -xcJob=BackupCatalog

While this feature might also be useful for other daemons, it can be applied to them in a later change.

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[alaaeddineelamri]

Thanks for your additions!

Everything is fine by me, just small details.