Flask App factory PR #1 (#8418)

* First cut at app factory

* Setting things back to master

* Working with new FLASK_APP

* Still need to refactor Celery

* CLI mostly working

* Working on unit tests

* Moving cli stuff around a bit

* Removing get in config

* Defaulting test config

* Adding flask-testing

* flask-testing casing

* resultsbackend property bug

* Fixing up cli

* Quick fix for KV api

* Working on save slice

* Fixed core_tests

* Fixed utils_tests

* Most tests working - still need to dig into remaining app_context issue in tests

* All tests passing locally - need to update code comments

* Fixing dashboard tests again

* Blacking

* Sorting imports

* linting

* removing envvar mangling

* blacking

* Fixing unit tests

* isorting

* licensing

* fixing mysql tests

* fixing cypress?

* fixing .flaskenv

* fixing test app_ctx

* fixing cypress

* moving manifest processor around

* moving results backend manager around

* Cleaning up __init__ a bit more

* Addressing PR comments

* Addressing PR comments

* Blacking

* Fixes for running celery worker

* Tuning isort

* Blacking

tests/security_tests.py

@@ -310,6 +310,7 @@ class RolePermissionTests(SupersetTestCase):
             ["Superset", "welcome"],
             ["SecurityApi", "login"],
             ["SecurityApi", "refresh"],
+            ["SupersetIndexView", "index"],
         ]
         unsecured_views = []
         for view_class in appbuilder.baseviews: