added ADC Module to Lizard

[JensOgorek]

Created a module that can read Analogue signals with the ESP32's ADC modules.
Crate ADC with adc = Adc() and read data with adc.read(adc_unit, channel, attenuation). The reading can be stopped with adc.stop() and the interval delay can be changed with adc.set_delay(value in ms) .
The exact GPIO to adc_channel configurations, attenuation levels and other requirements can be found in the ESP documentation.

Stable State:

• ESP works under the usual conditions
• ESP continues to work under the usual conditions while reading a signal with the ADC module
• ESP continues to work under the usual conditions after reading a signal with the ADC module and the module being stopped.
• ESP continues to work under the usual conditions when the reading of a pin failed (invalid parameters for the read or read_raw method).

Commit Messages:

• added read with voltage output
• added read_raw with bit output
• added set_delay
• added stop
• added docs
• added validation
• added module in callable modules
• changed misc

---

Feature request: #47

[falkoschindler]

As discussed with @JensOgorek, we'd like to simplify API and implementation like this:

adc = Adc(channel, number[, attenuation])

# or property?
adc.attenuation = 0
adc.attenuation = 2.5
adc.attenuation = 6
adc.attenuation = 11

# or set method?
adc.set_attenuation(11)

# step function writes data to properties:
adc.raw_value: integer
adc.voltage: number

[JensOgorek]

Updated to work with properties. The ADC module is now called like adc = Adc(channel, number[, attenuation]) and the values can be accessed with adc.raw_value and adc.voltage

[JensOgorek]

Changed the attenuation level input to match the attenuation db levels: 0, 2.5, 6 & 11