Compatibility to newznab offset parameter

According to https://newznab.readthedocs.org/en/latest/misc/api/

The client should take care of query multiple times with different offset parameter

[Response-offset field identifies the current subset of all the matches that are being transmitted in the response. In other words, if a search for “disco” finds more matches than the server is capable of transmitting in a single response, the response needs to be split into several responses. Then it is’s the clients responsibility to repeat the same query with same parameters but specify an increased offset in order to return the next set of results.]