Android 2.19.0

Google Play Notes:

• Watch and learn at your own pace by adjusting the video play speed controls.
• You can now choose to store downloaded videos in your SD card from the settings area.
• General improvements and bug fixes.

Diff:
edx/edx-app-android@rc/2.18.2...rc/2.19.0

Config:
https://github.com/edx/edx-mobile-config/commit/cbcfc44abc67c400f3cfb7ac137289d09de99446
(internal use)

Schedule:
09/05/2019 ~7:25 am EST: 20% Staged rollout
10/05/2019 ~9:00 am EST : 40% rollout
We didn't do 100% rollout of this release as we have planned v2.19.1 hotfix for it.