marctools 1.5.0

Changed json export format for marctojson.

The new format uses arrays for all subfield values,
not just for those, which had more than one element.

old: {"020": [{"a": "1234567890", "ind1": " ", "ind2": " ", "z": ["A", "B"]}]}
new: {"020": [{"a": ["1234567890"], "ind1": " ", "ind2": " ", "z": ["A", "B"]}]}

This unifies and hopefully simplifies processing on the consumer side.

Control field values are still just strings, since they are single values by spec.