* ColorSchemeControl: fixing bad use of PropTypes
Accessing PropTypes via the main React package is deprecated, and will be
removed in React v16.0. Use the latest available v15.* prop-types package from
npm instead. For info on usage, compatibility, migration and more, see
https://fb.me/prop-types-docs
* Control: adding PropTypes.func in types allowed inside `value` prop
This removes a warning during yarn tests
Fix#3589
* tests(QueryStateLabel): removing missing prop warning
```
Warning: Failed prop type: The prop `query` is marked as required in
`QueryStateLabel`, but its value is `undefined`.
in QueryStateLabel
```
* SaveQuery: removing invalid prop `target` supplied to `Overlay`.
This removes a warning during yarn tests:
```
Warning: Failed prop type: Invalid prop `target` supplied to `Overlay`.
```
* RunQueryActionButton: removing `isRequired` from queryState props
This removes a warning during yarn tests:
```
Warning: Failed prop type: The prop `queryState` is marked as required in
`RunQueryActionButton`, but its value is `null`.
```
* upgrade celery to 4.0.2
* using Redis for unit tests (sqla broker not supported in Celery 4)
* Setting Celery's soft_time_limit based on `SQLLAB_ASYNC_TIME_LIMIT_SEC` config
* Better error handling in async tasks
* Better statsd logging in async tasks
* show [pending/running] query status in Results tab
* systematically using sqla NullPool on worker (async) to limit number
of database connections
