public static FilterFieldDefinition defaultField(final String displayName,
                                                     final String filterQualifier) {
        return new FilterFieldDefinition(displayName, filterQualifier, true);
    }
Creates a field that is a default field which does not havee to be qualified. You can have multiple
default fields. If there are multiple then the predicate for each default field are OR'd together.

@param displayName     The display name or column heading for the field in the table.
@param filterQualifier The custom field qualifier used in the quick filter. Only use this if you want a
                       qualifier that is different from the display name. Should match ^[a-zA-Z0-9]+$
stroom-util-shared/src/main/java/stroom/util/shared/filter/FilterFieldDefinition.java