Resolve response errors

.../src/main/java/info/textgrid/middleware/ErrorHandler.java

.../textgrid/middleware/IdentifierListDelivererAbstract.java

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

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

...info/textgrid/middleware/RecordListDelivererAbstract.java

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

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