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/input/media/media.h

@@ -24,6 +24,8 @@
 #include "codec/decoder.h"
 #include "node/node.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A node that imports an image
  */
@@ -54,4 +56,6 @@ private slots:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // MEDIAINPUT_H