modbus write register service

[persandstrom]

Description:
New service to write modbus register.

Pull request in home-assistant.io with documentation (if applicable): home-assistant/home-assistant.io#834

Example entry for configuration.yaml (if applicable):

automation:
  - alias: Set fan speed                                                         
    trigger:                                                                     
      platform: state                                                            
      entity_id: input_slider.fan_speed                                                                         
    action:                                                                                                     
      service: modbus.write_register                                                                            
      data_template:                                                                                            
        unit: 1                                                                                                 
        address: 100                                                             
        value: '{{ states.input_slider.fan_speed.state }}'  

Checklist:

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

• Documentation added/updated in home-assistant.io

If code communicates with devices, web services, or a:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

[persandstrom]

@robbiet480 @MartinHjelmare could you have a look at this and get in into the release as well?

[robbiet480]

🐬

[persandstrom]

Thanks!