Setting to reduce mobile data usage

• Setting to toggle image / video loading. This would add a toggle to the Settings screen on the mobile app to enable a data saver mode. While data saver mode is enabled, videos and images in posts will not load unless explicitly clicked by a user. Images such as avatars and other small assets would not be affected.

• Investigate data usage tracker - It might be possible to track data usage inside the app. However, Twitter does not do this and Android at the least has a data tracker that displays data usage by app in Settings. I don't think this part would be necessary.

When enabled, Data-saver Mode will cause newsfeed items to load a placeholder that can be tapped to load the image.

• New section/screen under Settings called "Data Saver"
  • Checkbox to store a boolean for data-saver mode
  • Checkbox to store a boolean for disabling data-saver mode automatically when on WiFi

Mockups required before starting this task