[evcc] Extend accepted types for commands & Handle quantity types of commands (#13795)

[evcc] Extend accepted types for commands & Handle quantity types of commands (#13795)

* [evcc] Extend accepted command types
* [evcc] Convert QuantityType commands to required units
* [evcc] Allow evcc URL to end with a slash

Should fix an issue on the forum, where a user sent a command of DecimalType, but the binding expected a QuantityType.
See https://community.openhab.org/t/evcc-binding-electric-vehicle-charging-control/135209/15.
The accepted command types are extended for all channels if possible.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>