Fix failing test_import.py naming integration tests

For some reason, depending on the method used to run the tests, the Object:id
line is not always at the same position in the stderr. This commit applies the
same strategy as the one used in test.integration.library.import_image() i.e.
loop over the stderr lines (in reverse order) and break when a match is found.
Add test for integration arguments in bin/omero import
Add integration test for --annotation_link argument of CLI import
Isolate get_object() and get_annotation_link() in test_import.py
Add integration tests for screen/dataset arguments
Fix integration test for screen argument of CLI import

For some reasons, the fake SPW creates a screen at import so we must retrieve
all screens linked to the plate and make sure the linked screen is among them
Add docstrings to the CLI import test methods
Add ids to naming tests to improve displayed test names
Add integration tests for debug arguments in CLI import command

Test all debug levels from ALL to ERROR and check the output of the stdout.
As it stands, 2 elements need to be excluded from the debug level parsing: the
first two lines of the output which are always displayed at the INFO level and
the ome.system.UpgradeCheck logging.