add ability to render textures to Screen quad for dbg

include/openspace/rendering/renderengine.h

@@ -151,6 +151,8 @@ public:
      */
     static scripting::LuaLibrary luaLibrary();
 
+    void setDebugTextureRendering(GLuint texture);
+
     glm::ivec2 renderingResolution() const;
     glm::ivec2 fontResolution() const;
 
@@ -176,6 +178,8 @@ private:
     ghoul::Dictionary _resolveData;
     ScreenLog* _log = nullptr;
 
+    GLuint _debugTextureRender = 0;
+
     ghoul::opengl::OpenGLStateCache* _openglStateCache = nullptr;
 
     properties::BoolProperty _showOverlayOnClients;