qemuBuildMemoryDeviceCommandLine: Generate via JSON

qemuBuildMemoryDeviceCommandLine: Generate via JSON

This includes the 'pc-dimm', 'nvdimm', 'virtio-pmem-pci' and
'virtio-mem-pci' devices.

The value types according to QEMU are:

'pc-dimm'
  node=<uint32>          -  (default: 0)
  memdev=<link<memory-backend>>

'nvdimm'
  label-size=<int>
  memdev=<link<memory-backend>>
  node=<uint32>          -  (default: 0)
  unarmed=<bool>         -  (default: false)
  uuid=<QemuUUID>

'virtio-pmem-pci'
  memdev=<link<memory-backend>>

'virtio-mem-pci'
  block-size=<size>
  memdev=<link<memory-backend>>
  node=<uint32>          -  (default: 0)
  requested-size=<size>

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>