change default hyperkit binary name

rewrite for sanity

add hwrng device

fix version

add support for qcow disks

allow xhyve binary customisation

defaults to hyperkit

Version 0.4.0.

hyv 0.4.0 requires xhyve 0.2.0.

Version 0.3.0.

Note: hyv now uses an ini-style format instead of the old
colon-separated key-value pairs.

Update version.

Handle VM reboots.

xhyve, similar to bhyve, uses exit codes to let the caller handle
these events.