various: use simpler/smarter XML reading functions

Should address any XML parsing issues and allows for simpler, more maintainable
code. Should also address a crash that could occur when pasting nodes that had
inputs that weren't copied.

app/common/xmlutils.h

@@ -5,9 +5,6 @@
 
 #include "node/node.h"
 
-#define XMLReadLoop(reader, section) \
-  while (!reader->atEnd() && !(reader->name() == section && reader->isEndElement()) && reader->readNext())
-
 #define XMLAttributeLoop(reader, item) \
   QXmlStreamAttributes __attributes = reader->attributes(); \
   foreach (const QXmlStreamAttribute& item, __attributes)
@@ -16,4 +13,6 @@ Node *XMLLoadNode(QXmlStreamReader* reader);
 
 void XMLConnectNodes(const QHash<quintptr, NodeOutput *> &output_ptrs, const QList<NodeParam::SerializedConnection> &desired_connections);
 
+bool XMLReadNextStartElement(QXmlStreamReader* reader);
+
 #endif // XMLREADLOOP_H