Fix BlackMisc header includes

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

refs #630

src/blackmisc/pq/time.cpp

@@ -8,6 +8,10 @@
  */
 
 #include "blackmisc/pq/time.h"
+#include "blackmisc/math/mathutils.h"
+#include <QTime>
+#include <QtGlobal>
+#include <cmath>
 
 namespace BlackMisc
 {