Option to revert fan rotation speed scale
* **Please explain your feature request in a one or two sentences.**
add an option to revert #534 from levels to precentages via the config.


* **Is your feature request related to a problem? Please describe.**
While the change is visually better it seems that functionally it is less convenient for two reasons:
1. Asking Siri to set a certain fan level now causes her to always set it to max (level 3).
2. It is no longer possible to tap the slider in the home app to set a certain level and you are forced to actually use a sliding motion, also tapping the slider while the fan is on will always set it to off even if tapping the top of the slider.


* **Any particular eWeLink devices that this relates to?**
iFan


* **Anything else?**
I am guessing these issues are caused by HomeKit and Siri behavior and cannot overcome while keeping the 3 level display hence why I am asking for an option to choose between the two.

