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/nodeviewitem.h

@@ -31,6 +31,8 @@
 #include "nodeviewedge.h"
 #include "nodeviewitemwidgetproxy.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A visual widget representation of a Node object to be used in a NodeView
  *
@@ -153,4 +155,6 @@ private:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // NODEVIEWITEM_H