Data quality validation

[SimonKonar]

Negotiator pull request:

Description:

Add functionality which validates if the provided parsing_map has all the necessary data/attributes for correct transformation into the FHIR representation. This functionality also validates the file structure of the provided files for transformation( however, not every record(line) is validated, only if the necessary data/attributes as defined in parsing_map are present)

Checklist:

• [x] I have performed a self-review of my code
• [x] My code follows Google Python Style
• [x] I have made my code as simple as possible
• [x] I have added unit tests and the code coverage has not decreased
• [x] I have updated the documentation in all relevant places