Show LML host in data export for single VM.

TODO: Add the LMLHOST field while booting via pxelinux.pl so that we
could potentially share lab.conf between several LML hosts.
vmscreenshot.pl works now for any VM. If it does not exist in lab.conf
it will pull the needed UUID->MOREF mapping from vSphere.

Make LML::Lab return LML::VM objects instead of plain hashes. This is
the beginning of migrating LML::Lab to be more OO.
Merge branch 'master' of ssh://git@github.com/ImmobilienScout24/lab-manager-light.git