Add initial custom name property and support for more than one loadpoints

[Naiki92]

If you're using more than one instance, it may be useful to set an initial custom name. This PR reads the title from EVCC and sets it as the custom name. Changes in EVCC would then be reflected in VRM:

[tm-107]

I had to add these additional lines before line 140 to make it work:

config = self._getConfig()
deviceinstance = int(config['DEFAULT']['Deviceinstance'])
lpInstance = int(config['DEFAULT']['LoadpointInstance'])

Without these lines I always had the following error in the current.log:

2025-01-18 17:50:23,783 root CRITICAL Error at _update
Traceback (most recent call last):
  File "/data/dbus-evcc2/dbus-evcc.py", line 140, in _update
    loadpoint = result["loadpoints"][lpInstance]
NameError: name 'lpInstance' is not defined

Or have I overlooked something else?