VirualBox fails to resolve external hosts on some machines. Handle cases
when the host is behind a private network by making the NAT engine use the
host's resolver mechanisms to handle DNS requests.
They're now used only by the le-auto build process. The new public interface for OS-level bootstrapping is le-auto --os-packages-only, which dispatches by OS automatically. That obsoletes install-deps.sh as well, saving some repetition.
Also, switch to mustache-style templating to avoid colliding with shell variable references.
To optimize for the docker cache, we could later add a shim script that sources just deb_common.sh and calls its bootstrap function.
* Adds workaround to setup.py for issue with Vagrant sync filesystem and
hard linking (used by distutils in Python < 2.7.9). This workaround is
only used in a Vagrant environment.
* Adds Vagrant-related files to .gitignore
