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 think its better to just use the given input as the name without prepending 'provisioner.'.  It makes the behavior more consistent, otherwise we might end up with places in the code where somebody looks up 'log.directory' and other places where somebody looks up 'provisioner.log.directory'