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/projectexplorer/projectexplorertreeview.h

@@ -23,6 +23,10 @@
 
 #include <QTreeView>
 
+#include "common/define.h"
+
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief The view widget used when ProjectExplorer is in Tree View
  *
@@ -55,4 +59,6 @@ signals:
   void DoubleClickedEmptyArea();
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // PROJECTEXPLORERTREEVIEW_H