Fix BlackMisc header includes

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

refs #630

src/blackmisc/aviation/airport.cpp

@@ -8,9 +8,14 @@
  */
 
 #include "blackmisc/aviation/airport.h"
+#include "blackmisc/pq/angle.h"
 #include "blackmisc/propertyindex.h"
 #include "blackmisc/variant.h"
 
+#include <QCoreApplication>
+#include <Qt>
+#include <QtGlobal>
+
 using namespace BlackMisc::PhysicalQuantities;
 using namespace BlackMisc::Geo;