Bibsched: post-process data exchange

* Adds the ability for tasks to transfer data to BibTasklets specified
  via the `--post-process=` argument via a new parameter,
  `post-process_params` (e.g. the record ids processed).

Reviewed-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`.

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