Add I2c BH1750 light sensor for Raspberry Pi

[azogue]

Introduction:

Many of us use a Raspberry Pi to run Home Assistant, and we have different sensors connected to it, but for many of them there is no direct support, and it is necessary to use template sensors or command line sensors to make them work within Home Assistant.

Problem is using shell commands to retrieve the values of some sensors limits the working modes of these sensors, and, IMHO, it could be an entry barrier for some beginners.

I think that, as it exists for sensors like the DHT11/22 or the onewire ones, specific platforms for good and cheap digital sensors, with a simple configuration in Home Assistant, are very convenient.

This is the third of a series of PR that I intend to propose for supporting I2c digital sensors compatible with Raspberry Pi. First was #7989 (BME280 sensor), second was #8049 (HTU21D sensor), and this is the last (I don't have any more sensors to implement).

Description:

BH1750 sensor support as a sensor platform, with multiple working modes as described in its data sheet.
Senses the light level in lux.

The docs include a section to easy install the i2c and smbus support for the home_assistant user, to get things done quickly.

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#2821

Example entry for configuration.yaml (if applicable):

sensor:

  - platform: bh1750

A more complex, and customised configuration could be:

Example of customized configuration.yaml entry

sensor:

• platform: bh1750
  name: Light level
  i2c_address: 0x5c
  operation_mode: continuous_high_res_mode_2
  measurement_delay_ms: 30
  scan_interval: 10

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

[pvizeli]

Amazing work but it is not allow to have proto specific code inside HomeAssistant. Please export this device specific code into a new mini library and use this for this sensor.

[azogue]

@pvizeli, changes are done