prepare 'setup-storage' for easier testing and custom installation

 - remove hard-coded, absolute library path from bin/setup-storage
 - sanitize file layout
   (synchronize package name and filesystem location)

  lib/setup-storage/Commands.pm -> lib/perl5/Commands.pm
  lib/setup-storage/Exec.pm     -> lib/perl5/Exec.pm
  lib/setup-storage/Fstab.pm    -> lib/perl5/Fstab.pm
  lib/setup-storage/Init.pm     -> lib/perl5/Init.pm
  lib/setup-storage/Parser.pm   -> lib/perl5/Parser.pm
  lib/setup-storage/Sizes.pm    -> lib/perl5/Sizes.pm
  lib/setup-storage/Volumes.pm  -> lib/perl5/Volumes.pm
move informational header to the front and remove unnecessary versioning
information (git provides all the relevant data in much more detail)