avoid warnings when an info value is unset
avoid warnings when rpm-md repos are disabled
- Fixed --help output for disk-alignment
  The option value must be given in KBytes but the help did
  not explain that and the default value information used the
  wrong unit too
fix open3 usage
Merge pull request #377 from adrianschroeter/master

- Avoid unexpected warnings in product media code
- Support LUKS extension with LVM
- Add info messages for intermediate steps when creating the
  disk layout such like information about creation of md raid
  or luks extensions
- Call cryptsetup in one central encoding function in
  KIWIBoot for disk based images
- Added check for given type name on the commandline compared to
  the selected build type in the checkType global function.
  If the commandline specified type is valid but not specified
  in the configuration kiwi exits
- Don't call losetup with stderr redirected to stdout if the
  show option is used. potential error messages could then
  affect the standard output
- Make sure LUKS encoding is not applied if the given device
  already contains a LUKS container