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/panel/node/node.cpp

@@ -20,6 +20,8 @@
 
 #include "node.h"
 
+OLIVE_NAMESPACE_ENTER
+
 NodePanel::NodePanel(QWidget *parent) :
   PanelWidget(parent)
 {
@@ -88,3 +90,5 @@ void NodePanel::Retranslate()
 {
   SetTitle(tr("Node Editor"));
 }
+
+OLIVE_NAMESPACE_EXIT

app/panel/node/node.h

@@ -24,6 +24,8 @@
 #include "widget/nodeview/nodeview.h"
 #include "widget/panel/panel.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A PanelWidget wrapper around a NodeView
  */
@@ -62,4 +64,6 @@ private:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // NODEPANEL_H