Redesign blockly blocks for motor and sensor control

[JamesWP]

All interactions with motors, sensors, etc... should go though a simple hardware abstraction layer.

Devices will have one or more interfaces, each interface will have:

• a unique channel number
• be input or output (relative to the robot) (i.e. motors are output, sensors are input)
• be analogue or digital

This means we need only four blocks to interface with all things on the robot.

• Read Digital
• Write Digital
• Read Analogue
• Write Analogue

We should make this change in stages.

1. blockly blocks
2. vm function redesign
3. simulator core interface changes