Enhacement/75

This PR partially fixes the issue https://github.com/telefonicaid/fiware-connectors/issues/75 in the sense it re-implements the support for automatic Hive tables creation when simple attributes and empety metada are used in the Json persisted files. A new issue (https://github.com/telefonicaid/fiware-connectors/issues/89) has been created regarding release 0.4 in order to support complex attributes and non-empty metadata; this support requires the implementarion of a custom Json serde.

Tests:
* 100% unit tests.
* Manually tested with success.