Add user-defined category-label colors (#1402)

* Add user-defined category-label colors

Fixes https://github.com/chanzuckerberg/cellxgene/issues/1152

As described in https://github.com/chanzuckerberg/cellxgene/issues/1307

* Respond to feedback from @bkmartinjr in nodejs

* Respond to feedback from @bkmartinjr in python

* Add tests to the server module

* Autoformat python, run linter

* Make colors_get error handling specific

* Respond to feedback from @bkmartinjr

* Respond to feedback from @bkmartinjr

* Fix whitespace

* Fix python lint errrors

* Update documentation

* Add --disable-user-colors option to launch and cxgtool.py

* Fix python formatting

* Rename '--disable-user-colors' to '--disable-custom-colors'

server/test/test_anndata_adaptor_data_load.py

@@ -4,6 +4,7 @@ import json
 from server.data_anndata.anndata_adaptor import AnndataAdaptor
 from server.common.data_locator import DataLocator
 from server.common.app_config import AppConfig
+from server.test import PROJECT_ROOT
 
 
 class DataLoadAdaptorTest(unittest.TestCase):
@@ -12,7 +13,7 @@ class DataLoadAdaptorTest(unittest.TestCase):
     """
 
     def setUp(self):
-        self.data_file = DataLocator("../example-dataset/pbmc3k.h5ad")
+        self.data_file = DataLocator(f"{PROJECT_ROOT}/example-dataset/pbmc3k.h5ad")
         config = AppConfig()
         config.update(single_dataset__datapath=self.data_file.path)
         config.complete_config()