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.

Not only a move, also the strings are compared as string and not with 'size == 0'.
If the expect fails, the 'size == 0' gives no hints, while the string comparison tells you everything you need.
However, moving it from where it was to upwards was probably just a mistake.
Will be fixed.