Draft: Support QEmu local grid - DO NOT MERGE

Refers to #87 (closed)

This PR provides support for LibVirt/QEmu/KVM when deploying the local grid with vagrant and morph. And the support for Virtualbox has been removed. The documentation has been updated accordingly (see morph/grid/local/README.rst).

TODO: This branch is based on production to avoid a known issue on develop (with zkap). It should probably be rebased onto or merged with develop before review...