Remove max_batch from g.json even if it is None

Leaving it in would lead to a BAD_REQUEST error
Add filter option for hidden jobs

Hidden jobs are not shown by default.
Filter on / sort by jobtype
Merge pull request #265 from guidow/fix_max_batch_null_again

Remove max_batch from g.json even if it is None
Merge pull request #269 from guidow/hidden_jobs_filter

Add filter option for hidden jobs
Merge pull request #270 from guidow/filter_sort_by_jobtype

Filter on / sort by jobtype