Screenshots update

Update README.md

app/google-services.json edited online with Bitbucket

Foreground service implementation

Dependencies version updates

Renamed previousBearing collection to previousEvent

Renamed steps collection to device_events

Adds version info.

Adds static test data.

Implements forward bearings.

Using Location variable names in DB document.

Kotlin implementation.

Fixes worker start/stop implementation.

Added empty LocationWorker class.

Implements initial tracking service page flow.