Add options to write appinfo and manifest as JSON

[BOLL7708]

This to enable integration with automation suites that reads JSON files.

This is a replacement for my previous pull request that I closed. This is instead separated from previous functionality to not introduce complexity. This simply writes already downloaded app-info and manifest data to the config folder as JSON when downloading something.

It adds two new options;

1. -appinfo-json
2. -manifest-json