Add creation of LVM2 PVs (#670171)

Add creation of Physical Volumes specifying LVM2 metatdata format:
    lvm pvcreate -M 2 /dev/DEVICE

Also set the partition type to identify its contents as LVM.  Note that
libparted treats every partition type as a file system except LVM which
it treats as a flag, hence GParted displaying "lvm" in the Manage Flags
dialog.  Never the less libparted set the partition types correctly.
For MBR partitioning the type is 8e "Linux LVM" and for GPT partitioning
the type is E6D6D379-F507-44C2-A23C-238F2A3DF928.  Setting the partition
type as LVM is not strictly required as LVM2 scans the contents of all
partitions looking for PVs, but it is best practice.

Bug #670171 - Add LVM PV read-write support