Support for relay ports for LCN light platform

[alengwenus]

Description:

Support is added for lights which are connected to the relays of LCN hardware devices.

Related issue (if applicable):

Pull request in home-assistant.io with documentation (if applicable): home-assistant/home-assistant.io#7977

Example entry for configuration.yaml (if applicable):

lcn:
  connections:
    - name: myhome
      host: 192.168.2.41
      port: 4114
      username: !secret lcn_username
      password: !secret lcn_password

  lights:
    - name: Living room
      address: myhome.0.7
      output: relay1

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

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

• Documentation added/updated in home-assistant.io

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

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

[dgomes]

Looks good!

[MartinHjelmare]

Good!