Vagrant.configure is now how configuration is done in Vagrantfiles
(previously it was Vagrant::Config.run). This function takes a single
argument which is the version of configuration to use.
Various internals were updated for this new versioned configuration.
Note that multiple versions of configuration aren't yet used so aren't
fully supported by Vagrant, but the foundation is being set here.
I created VersionBase which is the abstract base class for any
configuration versions. Configuration versions are responsible for
knowing how to load configuration given a proc (from a
Vagrant.configure block), as well as merging configuration procs. In the
future, it will have to upgrade versions as well. This is not done yet.
The VERSIONS constant was added to Vagrant::Config which is a registry
to keep track of all the available configuration versions. The
VERSIONS_ORDER constant is an array of the ordering of these versions.
The ordering is important so that in the future Vagrant can attempt to
gracefully upgrade the configurations. It is also used to determine the
current configuration version (which is assumed to be the last version
in the order).
The loader was modified to use the current version and the VERSIONS
registry instead of hardcoding V1.
Config::Loader will be the new class responsible for loading configuration
and replaces the previous dual-role "Vagrant::Config" played. While this
commit is very early-stage, once this new architecture is flushed out, it
will make loading, using, and extending configuration much easier and cleaner.
Additionally, I believe this will help post Vagrant 1.0 if multi-language
configuration is implemented.
