adds extra verbosity option to ansible provisioner

Ansible has two levels of verbosity when running `ansible-playback`.  Vagrant supports `--vagrant` but not the more verbose `-vvv` option.  This patch exposes this flag to vagrant with an `config.extra_verbose = true` option.  It may be better to allow for `config.verbose = :extra` instead of adding the additional `extra_verbose` option.  Thoughts?  /cc @commandtab