support for thin LVs
Notable changes in this release:
- Create PVs with 128MiB of metadata, both through CreateVG and CreatePV. Default metadata size is 4MiB, which can be limiting.
- Add support for CreateLV with thin or thinpool.
- Simplify the hack for identifying SSDs by serial. It will no longer consider devices with 'ssd[0-9]' as ssd, but only 'ssd-'. Note that this really only applies to test with virtio as SSDs that are already identified by linux (via /sys/class/block//queue/rotational) will continue to be identified as such.