public void setSelectElementsBySummaryFeature(String summaryFeature) {
        selectElementsBySummaryFeature = summaryFeature;
    }
This class holds the extracted information after parsing a summary
field declaration, either from "field" inside "document-summary" or
"summary" inside "field".  Using simple data structures as far as
possible.  Do not put advanced logic here!
@author arnej27959
config-model/src/main/java/com/yahoo/schema/parser/ParsedSummaryField.java