Refactoring the driver class (backend source-incompatible)

Overview

A factory is creating instances of the driver class. Either it should be a sub-class of QSensor or it (or the factory) should create the QSensor instance. This is to help facilitate hacks where the client knows what driver is being used and accesses driver-specific stuff.

Implementation Plan

Update the API bits.

Update the unit test to verify the API bits.

Update the Qt Simulator backend.

Notes

I think the Qt Simulator backend lives in a QtSimulator repo.

Research Questions

Is a sub-class of the appropriate type the most suitable way of doing this? Is some other system more suitable?

Can the system cope when driver classes stop being sub-classes of QSensorBackend?