Added ISO-Date Getter function

Added Wrapper method for protected extractString method, for easy extension of ZUGFeRDImporter.java

libraryBasic/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDImporter.java

@@ -234,6 +234,25 @@ protected String extractString(String xpathStr) {
 	}
 
 
+	/**
+	 * Wrapper for protected method
+	 * @return the extracted String for the specific path in the document
+	 */
+	public String wExtractString(String xpathStr) {
+		return extractString(xpathStr);
+	}
+
+
+	/**
+	 * @return an ISO XXX coded datetime string
+	 */
+	public String getISOdate(String xpathString) {
+		String date = extractString(xpathString);
+		//do some conversion magic here
+		return date;
+	}
+
+
 	/**
 	 * @return the reference (purpose) the sender specified for this invoice
 	 */