- only require the uefi isohybrid command line option when building
  a EFI/UEFI iso
  + at present the uefi command line option on the isohybrid executable is
    treated as mandatory. This breaks all ISO builds on systems that do not
    have the latest isohybrid tool even if the ISO to be created is not
    designated as an efi/uefi ISO via the firmware attribute. The changes
    treat the uefi command line option as optional. A runtime check ensures
    that kiwi exits if the uefi command line option is required and the
    tool does not support it.
- new runtime check and test cases
- I removed the runtime check for xfs and reiserfs. reiserfs
  is more or less dead and xfs is a pure optional filesystem.
  If we have a mandatory check for xfs kiwi has to require the
  tools package on the package and on the build level which I
  think is not required. imho it would also be better to change
  the fstool runtime check to check only for the selected
  filesystem and not the complete list. We cannot expect our
  users to install all filesystem tools
- fixed use of undefined value in writeImageConfig