Rework XML Element hierarchy and XmlStringBuilder

- Reduce the amount of types that are subtypes of NamedElement. See
javadoc of NamedElement for rationale.
- Work more with XmlEnvironment in XmlStringBuilder.
- Some minor changes to XmlStringBuilder API.

smack-jingle-old/src/main/java/org/jivesoftware/smackx/jingleold/packet/Jingle.java

@@ -182,25 +182,6 @@ public class Jingle extends IQ {
         return sid;
     }
 
-    /**
-     * Returns the XML element name of the extension sub-packet root element.
-     * Always returns "jingle"
-     *
-     * @return the XML element name of the stanza extension.
-     */
-    public static String getElementName() {
-        return NODENAME;
-    }
-
-    /**
-     * Returns the XML namespace of the extension sub-packet root element.
-     *
-     * @return the XML namespace of the stanza extension.
-     */
-    public static String getNamespace() {
-        return NAMESPACE;
-    }
-
     /**
      * Jingle content info.
      *

smack-jingle-old/src/main/java/org/jivesoftware/smackx/jingleold/provider/JingleProvider.java

@@ -120,7 +120,7 @@ public class JingleProvider extends IQProvider<Jingle> {
                 }
 
             } else if (eventType == XmlPullParser.Event.END_ELEMENT) {
-                if (parser.getName().equals(Jingle.getElementName())) {
+                if (parser.getName().equals(Jingle.NODENAME)) {
                     done = true;
                 }
             }