BibSched: post-process data exchange

* Adds the ability for tasks to transfer arbitrary data to BibTasklets
  specified via the `--post-process=` argument 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>
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>