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/node/graph.h

@@ -25,6 +25,8 @@
 
 #include "node/node.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A collection of nodes
  */
@@ -90,4 +92,6 @@ private:
   QList<Node*> node_children_;
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // NODEGRAPH_H