various: encapsulate all code in the olive namespace to avoid name collisions

Large-scale code cleanup. Also adds a license to the top of all files that were
missing it.

app/widget/nodeview/nodeview.h

@@ -28,6 +28,8 @@
 #include "nodeviewscene.h"
 #include "widget/nodecopypaste/nodecopypaste.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A widget for viewing and editing node graphs
  *
@@ -117,4 +119,6 @@ private slots:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // NODEVIEW_H