Renamed the norelease plugin to no_release

The folder name has to be the same as the module_name, only then will we
be able to create a matching between the json data and plugin files.

This seems like a limitation but I can't think of anything better
either.
Added update capability to Gen JSON

If the json file exists it is first loaded and the already existing
entries are updated. Entries that don't exist are added.

Also added a download count field to all plugin entries.