experimental re-embedding (#1186)

* first cut at re-embedding route and back-end support

* update and expand config route tests

* add scanpy_umap

* add reembedding to config route parameters

* front-end support for reembedding fetch and UI

* remove unused imports

* add loading state

* save reembedding in reducer state

* improve withColsFrom

* transmit reembed schema to client; pick unique embedding names

* display embeddings

* format

* lint

* spaces, tab size 2

* lint

* test hack for smoke-test race

* back out hack sleep

* add check for backed mode

* add unit test for reembedding

* lint

* hide re-embedding CLI param from help

server/test/test_api.py

@@ -44,7 +44,7 @@ class EndPoints(object):
         result_data = result.json()
         self.assertIn("library_versions", result_data["config"])
         self.assertEqual(result_data["config"]["displayNames"]["dataset"], "pbmc3k")
-        self.assertEqual(len(result_data["config"]["features"]), 3)
+        self.assertEqual(len(result_data["config"]["features"]), 5)
 
     def test_get_layout_fbs(self):
         endpoint = "layout/obs"