add optional unique_id to manual config

[E4est]

fixes #197

This adds the ability to add the key unique_id to the integration when adding through configuration.yaml.

Sample:

media_player:
  - platform: samsungtv_tizen
    unique_id: media_player.samsung_tv_living_room
    name: 'Samsung TV living room'
    host: 192.168.178.4

This enables the "Settings" tab for the TV in the UI.

[victorigualada]

I need this too. Please merge that PR!

[LeandroSQ]

+1

[bchmura]

Thanks @E4est, I merged this in locally and it worked like a charm... thank you!