Merge branch 'examples_refactor' into viewport

# Conflicts:
#	examples/directx10_example/main.cpp
#	examples/directx11_example/main.cpp
#	examples/directx12_example/main.cpp
#	examples/opengl3_example/main.cpp
#	examples/sdl_opengl2_example/main.cpp
#	examples/sdl_opengl3_example/main.cpp
#	examples/sdl_vulkan_example/main.cpp
#	examples/vulkan_example/main.cpp
#	imgui.h

examples/opengl3_example/main.cpp

@@ -38,6 +38,7 @@ int main(int, char**)
     io.ConfigFlags |= ImGuiConfigFlags_MultiViewports;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
+
     ImGui_ImplGlfw_Init(window, true);
     ImGui_ImplOpenGL3_Init();