Use JSON file as input metadata

[sapoudel]

Use JSON file instead of csv/tsv as input metadata file.

Just talked to some of the people at DTU who developed anti-smash and they mentioned that using csv files can lead to unexpected outcomes/ errors that may be harder to catch when you start scaling your pipeline. Some of our most common errors arise from using this format. We should consider switching to JSON instead. This will require lots of changes:

1. Integrate json into Nextflow
2. Allow users to manually add things that are converted to json (maybe something like ALE sheets)
3. Add checks on data types