Ask for schema from data providers

See #25 , #70 (closed)

If we are to perform operations on the data being passed through PEDASI, we have to know the structure and types of that data. The simplest case - an probably sufficient for the majority of cases - would be to ask data providers for a JSON Schema for their data.

This schema would be a required piece of information to reach one of the quality levels (#70 (closed)).

This would allow:

• Data to be validated as 'schema conformant'
• Data to be processed, modified, or aggregated
  • e.g. detuning - data provider can ask for particular fields to be detuned in particular ways (max, min, mean, etc.)