"write bootstrap" & "full/diff backup pool"

[tmanninger]

Hi,

this merge request adds:

• support for the "write bootstrap" option in the job and jobdefs defination
• "full / differential backup pool" support for jobdefs.

bootstrap example:

  bacula::job { "host-job":
    jobdef    => 'default',
    ....
    write_bootstrap => '/srv/bacula/bootstraps/host',
  }

backup pool example:

    bacula::jobdefs { "default":
      ....
      full_backup_pool  => "full-pool"
    }

[zachfi]

This looks good, thank you. Would you mind also updating the README for the new option?