Fix BlackMisc header includes

* Include only what is used
* Use forward declaration when possible
* Sorted includes

refs #630

src/blackmisc/metadatautils.h

@@ -13,9 +13,14 @@
 #define BLACKMISC_METADATAUTILS_H
 
 #include "blackmisc/blackmiscexport.h"
-#include <QTextStream>
+
+#include <stddef.h>
 #include <QString>
 
+class QMetaType;
+class QTextStream;
+struct QMetaObject;
+
 //! Metadata util functions
 namespace BlackMisc
 {