Cleanup source tree

Move all C++ source files in the src subfolder. Adapted the cmake process accordingly and cleanup.

src/LayerView.h

@@ -0,0 +1,35 @@
+#ifndef LAYERVIEW_H
+#define LAYERVIEW_H
+
+#include "View.h"
+
+class LayerView : public View
+{
+public:
+    LayerView();
+    // non assignable class
+    LayerView(LayerView const&) = delete;
+    LayerView& operator=(LayerView const&) = delete;
+
+    void draw () override;
+    void update (float dt) override;
+    void resize (int) override;
+    int  size () override;
+    bool canSelect(Source *) override;
+
+    std::pair<Node *, glm::vec2> pick(glm::vec2) override;
+    Cursor grab (Source *s, glm::vec2 from, glm::vec2 to, std::pair<Node *, glm::vec2> pick) override;
+    void arrow (glm::vec2) override;
+
+    float setDepth (Source *, float d = -1.f);
+
+private:
+    void updateSelectionOverlay() override;
+
+    float aspect_ratio;
+    Mesh *persp_left_, *persp_right_;
+    Group *frame_;
+
+};
+
+#endif // LAYERVIEW_H