Backlog/112

Mainly implements issue https://github.com/telefonicaid/fiware-connectors/issues/112.

It implements issue https://github.com/telefonicaid/fiware-connectors/issues/104 as well.
That was my doubt as well. I decided to use ERROR because, in the end, this is an error, independently the code is able to solve it itself, and the user should notice about that.