Dynamically fetch rules to generate sample->summary and target->summary

[sveinugu]

sample_type->summary is generated based on a hard-coded map from biospecimen_class to a particular sample_type sub-property. This map might change in future versions of the standard, and it is thus better to dynamically fetch this map from the standard, where it is encoded as value=>required rules within the allOf rules in the sample schema.

Similar value=>required rules are encoded within the allOf part of the experiment schema, this time mapping from technique value to corresponding target sub-properties. In the current code, all target subproperties are looped through, and the first value found is copied to the summary property, which is an error-prone solution.

Not required for FAIRtracks v2.0, but would be nice.