Performance profiling: slow queries

[rsimon]

Figure out where the current bottlenecks are. E.g. the query "inscriptions" takes a long time to answer, even when the time histogram is not computed. Figure out where the slow bits are.

[rsimon]

Note: in case of inscription the response is 750kB, so delay might be due to sheer size - retrieval, entity resolution, JSON (de-)serialization, etc.