Task/395 pagination queries

### Description
Pagination implemented and with rudimentary unit tests.
URI params 'offset' and 'limit' used.
A third URI param 'details' steers whether 'mongo db count' command is issued on no hits.

Good point about comparing with "" instead of size == 0. There is a LOT of places in the unit test that are actually using size == 0 and could take advantajge of "". Maybe we should open an issue about this...