Feature/provisioner configfile

- [x] provisioner reads properties from a default config file, and optionally, an additional override file given with the ``-C <file>`` option
- [x] additional configs such as log rotation settings
- [x] removed all command line arguments except ``-C <configfile>`` and ``--register``
- [ ] we may consider changing config files to .rb... xml was just easy to implement first.
- [x] minor unrelated change: abort startup if unhandled exceptions in heartbeat thread
I don't think we need to enforce this. For example if we ever changed the provisioner to read directly from the queue instead of calling the server, we might have config settings that don't fit into this pattern.