Add analog module

[Gasper]

Analog module

This pull request brings API for using ADCs, DACs and hall sensor.

The examples build on the not-yet-merged serial API, so I'll keep this WIP, until that pull request is closed.

If you have any suggestions on how to improve the code, please let me know.

Tested

I tested the following:

• ADC1: pin 36, pin 39, pin 34, pin 35, pin 33, pin 32
• ADC2: pin 0, pin 2, pin 4, pin 12, pin 13, pin 14, pin 15, pin 25, pin 26, pin 27
• DAC1: pin 25
• DAC2: pin 26
• Hall sensor

I haven't tested:

• ADC1: pins 37 and 38, as I don't have them exposed on my board.

Not included

Some functionality related to analog subsystem of the chip is not included in this PR: cosine-wave generator, touch sensors, vref/two-point calibration

[Gasper]

Now that serial is merged, I rebased this to master and quickly tested it. As far as I'm concerned, it's ready for review.

[MabezDev]

This looks great! Thank you!