Changing database schema to allow empty `parameters` object

In the db JSON schema, it specifies that a set's parameters object must have at least one entry in it. I'd like to remove the minProperties restriction to allow this field to exist without having any entries in it.

Now that local editing is becoming a thing, people have access to the JSON metadata files. Having these fields exist even if they're empty allows the user to see these fields when they browse the metadata.

It also makes sense from a parsing POV, since having fields exist even when they're empty makes the data transformation easier, as well as allowing us to define a "skeleton" for these metadata objects.

@samuel.gaist would this change be viable?