- fixes for the oem partition install mode:
  * fixed check for amount of required partitions
  * removed check for partid, does not work well with GPT
  * fixed handling to be more generic and more independent
    from the number of partitions in the image. Using the
    filesystem label for selecting the partitions

- fixed runInteractive function and call params:
  * don't use --stdout option for dialog, the written result
    contains escape characters which confuses the code.
    Instead use the default stderr channel where dialog
    write its results