Added support for Netatmo rain gauge

Also, config is not automatically parsed in __init__ if _config already
has a value (e.g., from a child class). Finally, DB connection info is
not mandatory. An empty DB connection object will be created if
credentials are missing.
Added listNetatmoAPIStations() method

Get a list of Netatmo devices/modules as station objects for easier
automated setup.
Added explian and defaults for Netatmo rain gauge
Added delay option for logging DB handler

Default is to delay. Connection will not be opened until the first emit
is performed.
Expose default config file path as a constant

Path of default config file can be inspected without instantiating the
config parser.
Add auto-station config in Netatmo section

Stations can be added/updated based on the contents of the Netatmo API
after the Netatmo credentials have been added.
Config controller can be run without app.cfg

If app.cfg is missing when config controller is run (as it will be
during initial setup), then a skeleton config is loaded so that the app
still functions. This is only allowed during config setup as an
improperly configured data path, DB, or station list could be a bad
thing for other controllers.