Fix binding diff with prop group

[elihart]

Fix for #345

The generated logic for determining which props to update on a view now looks like this

if (assignedAttributes_epoxyGeneratedModel.get(3)) {
      if ((paddingRes_Int != that.paddingRes_Int)) {
        object.setPaddingRes(paddingRes_Int);
      }
    }
    else if (assignedAttributes_epoxyGeneratedModel.get(4)) {
      if ((paddingDp_Int != that.paddingDp_Int)) {
        object.setPaddingDp(paddingDp_Int);
      }
    }
    // A value was not set so we should use the default value, but we only need to set it if the previous model had a custom value set.
    else if (that.assignedAttributes_epoxyGeneratedModel.get(3) || that.assignedAttributes_epoxyGeneratedModel.get(4)) {
      object.setPaddingDp(paddingDp_Int);
    }

    if ((hasFixedSize_Boolean != that.hasFixedSize_Boolean)) {
      object.setHasFixedSize(hasFixedSize_Boolean);
    }

    if (assignedAttributes_epoxyGeneratedModel.get(1)) {
      if ((Float.compare(that.numViewsToShowOnScreen_Float, numViewsToShowOnScreen_Float) != 0)) {
        object.setNumViewsToShowOnScreen(numViewsToShowOnScreen_Float);
      }
    }
    else if (assignedAttributes_epoxyGeneratedModel.get(2)) {
      if ((initialPrefetchItemCount_Int != that.initialPrefetchItemCount_Int)) {
        object.setInitialPrefetchItemCount(initialPrefetchItemCount_Int);
      }
    }
    // A value was not set so we should use the default value, but we only need to set it if the previous model had a custom value set.
    else if (that.assignedAttributes_epoxyGeneratedModel.get(1) || that.assignedAttributes_epoxyGeneratedModel.get(2)) {
      object.setNumViewsToShowOnScreen(numViewsToShowOnScreen_Float);
    }

    if ((models_List != null ? !models_List.equals(that.models_List) : that.models_List != null)) {
      object.setModels(models_List);
    }

This example comes from the CarouselModel_ code.