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 ... Some day ...
An issue would be good.
Things normally don't fail, but when they do, the string comparison is pretty much needed.
I only changed it in this place to understand the problem.