LEI-106: Enrich serializers by reverse lookup fields that allow bi-directional browsing through item references.

Task SW-415: Fixed Django ORM tests that failed due to enabled pagination and test env setup that is only required for functional API tests

SW-415: use same setup and teardown as in t_lsmrapp_scheduling_functional. TODO: create common bash file with setup/teardown routines.

SW-415: use same setup and teardown as in t_lsmrapp_scheduling_functional. TODO: create common bash file with setup/teardown routines.

SW-415: use same setup and teardown as in t_lsmrapp_specification_functional. TODO: create common bash file with setup/teardown routines.

SW-415: do not overwrite file, but append to it if existing. Issue warning to fill in the new credentials

SW-415: converted SAS/LSMR/bin/lsmr_testdatabase to python script, and added signal handlers to properly close the test postgres server

SW-415: automatically create dbcredentials file with sane defaults when no credentials are found. added tests.