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

superset/sql_lab.py

@@ -42,9 +42,9 @@ from superset import (
 )
 from superset.dataframe import SupersetDataFrame
 from superset.db_engine_specs import BaseEngineSpec
+from superset.extensions import celery_app
 from superset.models.sql_lab import Query
 from superset.sql_parse import ParsedQuery
-from superset.tasks.celery_app import app as celery_app
 from superset.utils.core import json_iso_dttm_ser, QueryStatus, sources, zlib_compress
 from superset.utils.dates import now_as_float
 from superset.utils.decorators import stats_timing