Fixed EC2 no more mkinitrd for 13.1 branch 

 - modify the way we create an EC2 image
  + prior to this change the initrd for an EC2 image was created with
     mkinitrd as mkinitrd changes got introduced that require a live root
     filesystem using mkinitrd is no longer feasible. The same situation
     applies as things move to dracut
   + we now use a kiwi generated initrd for a vmx image type, and modify
     specific files (menu.lst, bootloader setup, inittab) in the image
     to make the image ec2 specific
   + this change requires the use of different EC2 akis, we need to use
     an aki designated for a partitioned image hd00 designation
   + using the VMX build type creates a partitioned image, thus we need to
     use a different device mapping when creating the ec2-bundle, use
     ami=sda instead of ami=sda1 - update the unit tests to reflect
     the changes
- EC2 XML validation now checks that the image type is VMX instead of a
  filesystem
   + this is somewhat superfluous as it is more intuitive to build an EC2
     image as VMX. However as the previous type requirement was a file system
     we want to catch this and let people know if the config is incorrect.
- Use GPT partition for EC2
   + Amazon is transitioning to expecting GPT, thus we need to follow suit
- update the 12.2 and 12.3 examples to reflect the new build type settings
  for ec2 images
- add an ec2 example for 13.1
- include commit aba2000d946e1cf5d577a625c1cbfcab218fad7d from master
  chery-pick failed, thus no separate commit