WebSearch: use author IDs in self-cite math

• Uses bibauthorid to look for self-citations to fetch all records for a particular author, when author IDs are available. Otherwise falls back to the previous name based system.

• Adds 3 tests to verify that compute_self_citations behaves properly in at least 3 scenarios: no self-citations, one self-citation, only self-citations. Adds 1 global regression test case for the demo site conditions.

• Adds explanations on how self-citations are computed on citesummary help page.