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/menu/menushared.h

@@ -23,6 +23,8 @@
 
 #include "widget/menu/menu.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A static object that provides various "stock" menus for use throughout the application
  */
@@ -103,4 +105,6 @@ private slots:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // MENUSHARED_H