add an option to enable sections from extras tab in txt2img/img2img

fix some style inconsistenices

modules/shared_items.py

@@ -0,0 +1,10 @@
+
+
+def realesrgan_models_names():
+    import modules.realesrgan_model
+    return [x.name for x in modules.realesrgan_model.get_realesrgan_models(None)]
+
+def postprocessing_scripts():
+    import modules.scripts
+
+    return modules.scripts.scripts_postproc.scripts