Introduced machine state handlers (check and run still need work).

Added proper init handler, fetching settings and parameters and exposing them to UI.
Added spindle rendering.

render.h

@@ -15,17 +15,27 @@ public:
     void render(glm::mat4 mvp, glm::vec2 viewport_size);
 
     glm::vec3 get_extents_min() const { return min_pos; };
+
     glm::vec3 get_extents_max() const { return max_pos; };
 
 private:
     GLsizei build_vbo(const grbl::program& pgm);
 
+    GLuint spindle_vbo_id;
+    GLuint spindle_vao_id;
+
     GLuint vbo_id;
     GLuint vao_id;
+
     shader_program *shader = nullptr;
+
     bool initialized = false;
-    glm::vec3 min_pos, max_pos;
-    GLsizei vertices_count;
+
+    glm::vec3 min_pos, max_pos, spindle_pos;
+    GLsizei vertices_count, spindle_vertices_count;
+
+    void initialize_program_buffers();
+    void initialize_spindle_buffers();
 };