diffexp limit UI and configuration (#1336)

* warning on maxCount for diffexp

* cleanup logging

* clarification

* make the limits configurable

* make diff exp limit work

* danger!

* remove debugging code

* fix merge with master

* fix unit tests

Co-authored-by: Colin Megill <colinmegill@gmail.com>

server/test/test_anndata_adaptor.py

@@ -41,11 +41,11 @@ class AdaptorTest(unittest.TestCase):
             "diffexp__lfc_cutoff": 0.01,
             "adaptor__anndata_adaptor__backed": self.backed,
             "single_dataset__datapath": self.data_locator,
+            "limits__diffexp_cellcount_max": None,
+            "limits__column_request_max": None
         }
         config = AppConfig()
         config.update(**args)
-        for k in config.limits.keys():
-            config.limits[k] = None
         config.complete_config()
         self.data = AnndataAdaptor(DataLocator(self.data_locator), config)