Implements additional data sources for configuration

* Added data source base class
* Modified BaseConfigSectionInterface to be a pass through
  for data sources
* Refactored existing config into a ConfigParser data source
* Added JSON and Mongo data sources
* Note that this is just an architectual refactor. There is
  currently no means to use a different data source other
  than to manually change the data source type in
  BaseConfigSectionInterface. The pull request for having
  the data source be configurable will come seperately.

Change-Id: Ifb25fcdf627b0e9c5bad39f4a35309485d8495d7
Merge "Implements additional data sources for configuration"