Missing functions in Contact object

The Contact object defines some macros:

```
    macros = {
        'CONTACTNAME': 'contact_name',
        'CONTACTALIAS': 'alias',
        ...
        'CONTACTGROUPNAME': 'get_groupname',
        'CONTACTGROUPNAMES': 'get_groupnames'
    }
```

but the functions **get_groupname** and **get_groupnames** are not defined in the Contact class nor in the Item base class !
