API - OR / AND in search endpoint

[envycontent]

It isn't possible to search for all the talks with an organizing_department of x together with all the talks in the series Y. The talks returned will have both characteristics, not one or the other.

This kind of makes sense, but causes a few problems since we're more likely to be wanting to expand a search rather than narrow it down. E.g 'give me all talks in the Department of Scientific study of pigs' and the talks in this series 'A history of Pig Keeping', rather than all talks that are in the History of pig keeping and also organized by the department of scientific study.