added function to generate a map of parameter names and indicies

The intent here is to generate a map of parameter names and their indexes for each service method , eg:

```java
public static final Map<String, Integer> getBill_paramMap = new HashMap<String, Integer>(){{
      put("methodContext", 0);
      put("id", 1);
      put("billUid", 2);
      put("fields", 3);
    }};
```
Such that something doing some sort of central dispatching can be sure that it's putting the named parameters in the correct place.