Update vmx|oemboot descriptions for SLE12 / Factory

Make sure grub2-x86_64-xen is installed if a xen or ec2
profile is in use and the architecture is x86_64
Add grub2 modules for lvm and btrfs/xfs filesystems on demand
Update JeOS templates for SLE12 / Factory

Fix ec2 type to use the correct loader and firmware setup
Make use of LVM without boot partition as an example for the vmx type