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/projectexplorernavigation.h

@@ -26,6 +26,10 @@
 #include <QSlider>
 #include <QWidget>
 
+#include "common/define.h"
+
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A navigation bar widget for ProjectExplorer's Icon and List views
  *
@@ -108,4 +112,6 @@ private:
   QSlider* size_slider_;
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // PROJECTEXPLORERLISTVIEWTOOLBAR_H