remove ui namespace which is not really used, move CameraData in camera_modes.h to avoid the inclusion of canva.h

src/node_canvas.h

@@ -5,13 +5,13 @@
 class NodeCanvas : public Node
 {
 public:
-    std::unique_ptr<ui::Canvas> m_canvas;
+    std::unique_ptr<Canvas> m_canvas;
     Sampler m_sampler;
     Sampler m_sampler_linear;
     Sampler m_sampler_stencil;
-    ui::Plane m_face_plane;
-    ui::LineSegment m_line;
-    ui::Plane m_grid;
+    Plane m_face_plane;
+    LineSegment m_line;
+    Plane m_grid;
     int m_grid_divs = 30;
     virtual Node* clone_instantiate() const override;
     virtual void init() override;