[Bug] IDs are always made up of 6 hexadecimal characters 
**Describe the bug**
The doc says "IDs are always made up of 6 hexadecimal characters".

My new Shelly 2.5 id has 12 hexadecimal characters.

**Environment:**
 - Shelly device(s): Shelly 2.5
 - Plugin version: 0.15.6
 - Device running homebridge: Raspberry Pi

![image](https://user-images.githubusercontent.com/190756/96547209-fc81ba80-12ab-11eb-9a8b-36be0fd7d395.png)
