WebSearch: webcoll post-process data

• Adds sending of added/modified record IDs during webcoll run to post-process tasklet via a new task parameter post-process_params.

Co-authored-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>