The purpose of this new crate is to provide a common library to all
vhost-user backend implementations. The more is handled by this library,
the less duplication will need to happen in each vhost-user daemon.
This crate relies a lot on vhost_rs, vm-memory and vm-virtio crates.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>