annotations CLI and file UX rework (#1049)

* rename config param label-file

* annotations rework - CLI params, file naming and backups

* lint

* improve cli option error checks

* enable session cookies

* enable session cookies

* add session id

* name annotations file in multi-dataset and multi-user safe manner

* pass data user hash to front-end

* add annotation collection name support to front-end

* add constant for annotation data collection name

* parameterize annotation collection name; make it sticky in the session

* clarify comments

* hard wire a temporary data collection name for testing

* prettier

* test comment

* package command

* set annotations  filename dialog

* name  and hash are visible

* wire up data collection capture

server/test/test_scanpy_engine_data_load.py

@@ -24,7 +24,9 @@ class DataLoadEngineTest(unittest.TestCase):
             "obs_names": "foo",
             "var_names": "bar",
             "diffexp_lfc_cutoff": 0.1,
-            "label_file": None,
+            "annotations": False,
+            "annotations_file": None,
+            "annotations_output_dir": None,
             "backed": False,
             "diffexp_may_be_slow": False,
             "disable_diffexp": False