New input format

The big picture would be the ability to serialize and deserialize an instance at every stage, to enable backups and define how data can be imported.

In detail what I want to do is:

• Two JSON files for meta data and student submissions
• Additional data con be included via path in json
• The populate script should be declared deprecated and replaced by deserializers that work with #16 (closed).
• The converter scripts need a minor update