Bug/Feature fixes:

 1. Finally fix changing level on a dimmable device.
 2. Resuse the level from the last time the device was turned on.
    (does not work between restarts of the Steward).
Really turn the switch off.

 If only setting the level to 0, it is still considered to be on.
Change the number of significant digts, as per discussion in #227.
Merge pull request #249 from torkelsson/telldus-weather

Change the number of significant digts, as per discussion in #227.
Merge pull request #248 from torkelsson/telldus-debug

Telldus dimmable devices