Export Settings underlying settingsMap

Exposing the underlying map behind the settings struct now affords us
the ability to directly unmarshal JSON into `&settingsMap`. This
unmarshaling behaviour was attempted in lime, but was not working
properly due to attempting to unmarshal into the Settings struct as
opposed to the actual underlying map.

This change works with a change to lime, where a pointer to the
settingsMap is passed into the JSON unmarshaler allowing the parsing and
retrieval of config values.