User Interface reorganization

Revamp the user interface. Now the basic flow is:

• Welcome screen (one time)
• Main screen with subscreens:
  • News (placeholder)
  • Import (placeholder)
  • Export (placeholder)

Initial APK for Play store

Used to generate the very first APK submitted to the Google Play store. It implements the basic functionality:

• React Native framework
• Basic icon
• Initial Welcome screen with Opt In button
• Main screen with Opt Out button

After opting in, location snapshots are captured periodically in the background.