making fields for GetRecordList and RecordList configurable

...c/main/java/info/textgrid/middleware/DARIAHConstants.java

.../java/info/textgrid/middleware/DublinCoreFieldLoader.java

...re/src/main/java/info/textgrid/middleware/OAIPMHImpl.java

...c/main/java/info/textgrid/middleware/RecordDeliverer.java

...in/java/info/textgrid/middleware/RecordListDeliverer.java

...main/java/info/textgrid/middleware/RepIdentification.java

...e/src/main/java/info/textgrid/middleware/TGConstants.java

...re/src/test/java/info/textgrid/middleware/OaiPmhTest.java

oaipmh-webapp/src/main/webapp/WEB-INF/beans.xml