Construct the configuration file. Config file is looked for in three locations:
ENV lib/Mojito/conf/mojito_local.conf lib/Mojito/conf/mojito.conf The values will be merged with the precedent order being: ENV over mojito_local.conf over mojito.conf
Args: a configuration file name Returns: a HashRef of configuration values
Args: ($hash_ref_dominant, $hash_ref_subordinate) Returns: HashRef of the two merged with the dominant values chosen when they exist otherwise the subordinate values are used.