- Rework some of the autochanger data so that the DIR has

- Rework some of the autochanger data so that the DIR has
  the number of drives.
- Modify the way the Device info is returned so that it comes
  back as a special message type and can be sent anytime the
  Device status changes.
- Copy the change name and changer command into the device
  record if none is specified.
- Require the change command and changer name to be specified in
  and AutoChanger resource.
- Force all the Media Type records of all devices in an Autochanger
  to be the same.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@1873 91ce42f0-d328-0410-95d8-f526ca767f89