function to retrieve previous requests combined with get_single_request_data() so available to all views (search, results, report, etc); extended outstanding lab-tests display to unreported & unauthorised worklists
aded ability to link lab tests; moved Moose attribute lab_test_map from M::Result to M::R::LabTestUpdate - also used by M::R::ResultUpdate, but relies on caller also loading M::R::LabTestUpdate; new test script to test linked lab-tests
