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. ```name``` is the new attribute that is used to discover and route to this interface. This interface name is applied from the config and is the name of the definition block of the the interface. 
you already support it as an argument: https://github.com/deliveryhero/lymph/pull/37/files#diff-8a6086eb1e8566975ef71c7b6ca2051fR70