Allows multiple entries to be added for the integration

[stau]

Currently the DOMAIN (uponor) is set as the unique_id. This prevents multiple entries to be added.

Users can now optionally set a unique_id of their own preference or leave the field empty for it to be auto-generated.

The async_setup in __init__.py has been disabled, and seems like dead code.

Disclaimer: I am not familiar with Python and very inexperienced with the custom_component things in HA. Open to suggestions / improvements.

Fixes #34