Add support for arguments to vagrant provision to be passed through to beetbox.sh

[Decipher]

With the addition of overridable and custom playbooks/roles support in Beetbox, and the additon of arguments to be supplied to beetbox.sh to trigger specific playbooks, the logical next step is to add support for arguments to vagrant provision to be passed through to beetbox.sh.

In addition, the default playbook to be run when no argument is supplied should be configurable in the relevant config.yml file.

This would allow for users to default to a build only provision step while still allow a full provision by running vagrant provision provision (although the naming could be improved).

[thom8]

Fixed via #316