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/output.cpp

@@ -23,6 +23,8 @@
 #include "common/xmlutils.h"
 #include "node/node.h"
 
+OLIVE_NAMESPACE_ENTER
+
 NodeOutput::NodeOutput(const QString &id) :
   NodeParam(id)
 {
@@ -69,3 +71,5 @@ void NodeOutput::Save(QXmlStreamWriter *writer) const
 
   writer->writeEndElement(); // output
 }
+
+OLIVE_NAMESPACE_EXIT