Taking the service name from the config file

```
interfaces:
    restaurant_storage: # this should be the name of the interface (instead of lymph.Interface.service_type)
        class: dhh.storage.restaurants.interface:RestaurantStorage
    order_storage:
        class: dhh.mock:Mock
    user_storage:
        class: dhh.mock:Mock
```

Now you can't specify ```service_type``` anymore to your interfaces. The ```service_name``` is the new attribute that is used to discover and route to this interface. This service_name is applied from the config and is the name of the definition block of the the interface. 
I suggest:
_``name`` is an instance attribute which is taken from the config of the interface._

Why _usually_ so often? What other ways are there?