Feature:
 Ability to specify zlib or lzo compression.
  via 'vtlcmd' at runtime.
      'vtlcmd <> compression lzo'
      'vtlcmd <> compression zlib'
  or
  /etc/mhvtl/device.conf entry
      ' Compression type: lzo'
      ' Compression type: zlib'

Signed-off-by: Mark Harvey <markh794@gmail.com>