How To Develop a Device Driver

[LeStarch]

Pattern

In F Prime, what is typically called a "device driver" is broken down into two parts:

1. A device manager (e.g. Bmp280Manager) that provides device specific functionality and
2. A generic bus driver (e.g. I2cDriver) that manages the wire protocol

We should document both of these steps.

Rationale

This is common feedback, however; it is believed that the community writ-large wants part 1, and advanced users who provided the original feedback wanted part 2.

Thus we should do both.