Tantivy query parameters

*(In the tantivy branch)* make `content.query` accept parameters, like count, search fields or others. These are possible options:
- the query string and a parameters object
- a parameters object with q as the query string, maybe if only a string is passed `{q=arg}` is assumed
- both?
- if the set of possible parameters is really small and stable (unlikely IMO), positional arguments could also work