Down-sample sensor data in the API

If an application is reading a sensor at lower-than-native rate there may be aliasing effects. To deal with this, down-sampling needs to be done. To avoid apps having to do this, the API should be able to do this.

This needs to be an opt-in feature as down-sampling will cost CPU (battery).

Acceptance Criteria

• Unit test that verifies down-sampling logic works correctly.