provide tool to read batch job config

[jangalinski]

To support any possible batch job configuration, this extension chose to store the config in the byte_array db table (which is fine).
Problem: it is not possible to analyse failed jobs, because the configuration field in the DB just contains a pointer to a byte array entry which json content contains an encoded String, which is not human readable.

I was able to read the config by decoding the json strings selected from the DB .. but it took some effort and additional coding.

Idea: Provide a service, where I can enter the job id and get the json config. Additionally: provide a service where I pass the batch id and get the config of all contained jobs.