Remove bearing and tilt from the qml API

Bearing and tilt are rather far away from a working state.
This patch removes them from the public qml API and the documentation.

Change-Id: I820fed3f1acf9a05e250e474bf3ac35fcb6fc19f
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>