Add support for config file

[paller]

It should be possible to define the house layout with regards to what channels and sensors are related to a room. Something along the lines:

rooms:
  kitchen:
    sensors:
      - 12
      - 13
    channels:
      - 5
  bedroom:
    sensors:
      - 1
    channels:
      - 3

It might be possible to automatically detect and group channels and sensors only be assignment of a page id.

rooms:
  kitchen:
    page:
      - 1
  bedroom:
    page:
      - 2

[Abildgren]

This would make it very easy configure