add class parameters to configure default_settings.py

This commit adds class parameters to the puppetboard class to
automatically setup the puppetboard configuration file default_settings.py

The following parameters were added:

```
  $puppetdb_host = 'localhost'
  $puppetdb_port = 8080
  $puppetdb_key = 'None'
  $puppetdb_ssl = 'False'
  $puppetdb_cert = 'None'
  $puppetdb_timeout = 20
  $dev_listen_host = '127.0.0.1'
  $dev_listen_port = 5000
  $unresponsive = 3
  $enable_query = 'True'
  $python_loglevel = 'info'
```

The experimental parameter changed from true/false to a string
to support the Python bool True/False:

    $experimental = 'False'