WebFormFieldOrColumn.getList
        Returns the list associated with the form field or null if no list exists.
 The list can be one of three types: 
 
        - DynamicList - values are retrieved from a database
 - StaticList - supports multiple languages, values are defined using the Ebase Xi Designer
 - CustomList - the list is created programmatically using the #createCustomList() method
 
returns FieldList