Issues 2 4 improving array csv flattening

New improvements

1- We are now adding rows for relationships. Closes #4 (closed). 2- When the schema is a farmos convention we will extractt the internal data relations and list them under the new field convention_data_targets.

This is covered by the new tests "Relationships are parsed." and "$anyOf relationships in conventions are parsed".

IMPORTANT For this features to work, you need to parse with 'true' in the attribute isConvention, a new, second argument to flattenJSONSchema. If your shema object is called myFarmOSConvention, you would then do flattenJSONSchema(schema=myFarmOSConvention,isConvention=true) or flattenJSONSchema(myFarmOSConvention, true).