ConfigFile should support standard fields

[dmwhitne-583]

The ConfigFile class allows for a user to define a Message definition, and I suppose a Message definition could be used to define a list of standard fields that can be applied to a MessageFactory object, however this seems counterintuitive. After all, the user would need to lookup the message, then acquire the field iterator, and then add each field to a list, which can then finally be passed to MessageFactory setStandardFields().

It would be nice if the ConfigFile could ingest XML content representing a list of standard fields, and then have ConfigFile provide a method to return these fields in a List (of Field objects). For example:

<DEFINITIONS>
    <STANDARD-FIELDS name="My Mission Faves">
        <FIELD NAME="DOMAIN1" TYPE="STRING" HEADER="T">MY-DOM-1</FIELD>
        <FIELD NAME="DOMAIN2" TYPE="STRING" HEADER="T">MY-DOM-2</FIELD>
        <FIELD NAME="MISSION-ID" TYPE="STRING" HEADER="T">MY-MISSION</FIELD>
        ...
    </STANDARD-FIELDS>
</DEFINITIONS>

ConfigFile cf = new ConfigFile();
cf.load("MyDefinitions.xml");
messageFactory.setStandardFields( cf.getStandardFields("My Mission Faves") );