Add generic json reader

[Noordsestern]

Adding issue for provided PR.

a simple json-reader creating test data from any JSON file. Basically generic-csv-reader, but for json

The use case is data provided by APIs that is structured and well formatted. For using it with the original json-reader someone would have to put it in the Test Case Name - Tags - Arguments format which is complicated to automate. For working with not-explicit test data, the generic json reader is more flexible.