First Version to successfully work with DigiPot _and_ ToF Sensor.

Button-Press will set the currently measured distance as switching distance.
Does not yet save distance in EEPROM.

Incorporates single, static MuteProfile (see config.hpp).
On-Ramp time:  10 ms
Off-Ramp    : 200 ms
Max dampening.

Does not yet save MuteProfile in EEPROM.

Main Trick to fit everything into an attiny88 with 512 byte RAM: Compiling with -O2 instead of -Os.
This trades Flash size with RAM size. Stack usage is unknown, but estimated to be ~100 byte peak.

```
RAM:   [==        ]  21.1% (used 108 bytes from 512 bytes)
Flash: [========= ]  93.6% (used 7666 bytes from 8192 bytes)
```

Same changelog as v3.0.0 applies.

First version that will be sent to the manufacturers.

Changelog:

  - Dropped support of mimu_batt
  - Added Digipot-functionality

TODO:
Add SW support for changing mute profiles

PCB sent to production

 - Added attenuator
 - Button instead of Pot
 - PCB smaller outline
 - Red/Green LED

TODO:
 - Firmware should reflect HW changes

This is a working prototype.

Main features are demonstrated:
 - Battery usage minimal (days of runtime)
 - Phantom powered usage with no audible noise
 - Suitable range with more or less no impact of exteriour lights on TOF
 - Cheap BOM
TODO:
 - More or less variable dampening
 - Button instead of potentiometer
 - Even emaller outline
 - Three colored LED