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.

Yeah, why not.
It never hurts, even if the current implementation of the function to where it is sent always updates the variable.
That function may change in the future.
Good point.