Deprecate "details" mask.

Many reasons…

- it doesn't work
- it is so scale-sensitive that it makes the "scale to window" zoom level useless and behaves very differently depending on zoom level
- it is designed as a work-around for bad edge-avoidance in frequency modules - that should be fixed in those modules
- it samples data at demosaicing step, meaning later distortions mess it up and it's not available for non-raw images
- it is broken in many subtle ways. See #394

src/develop/blend_gui.c

@@ -2853,7 +2853,8 @@ void dt_iop_gui_update_blending(dt_iop_module_t *module)
   }
 
   const dt_image_t img = module->dev->image_storage;
-  gtk_widget_set_visible(bd->details_slider, dt_image_is_rawprepare_supported(&img));
+  // Details mask is deprecated. Show it only if it was used in an old edit
+  gtk_widget_set_visible(bd->details_slider, dt_image_is_rawprepare_supported(&img) && (module->blend_params->details != 0.0f));
 
   if((mask_mode & DEVELOP_MASK_ENABLED)
      && ((bd->masks_inited && (mask_mode & DEVELOP_MASK_MASK))