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}
git-svn-id: https://jti.org.uk/svn/hmds_lims/trunk@1839 4177bd82-f056-0410-812d-caef170e3fa0
