Bringing back ShadowTheAge#158:

It would be nice to be able to create nested tables that don't have a specific recipe they collapse to but rather a text title one can specify yourself.
Possibly one could also add an icon, to create kind of a "fake" recipe as a header for the table.

Reason: Sometimes i want to move different stuff onto the same sheet, but keep it organized into the different parts of the factory (e.g. petrochem, refining, smelting, ...). Having it on the same sheet allows to keep links for input and output, while still having custom names and headers to easily seperate them.
I don't want to use a specific recipe, because i might want an icon that is more general, bu is no recipe / a recipe i don't need at all. Another alternative would be to enable setting the building count to 0 so the recipe is not used, but something that looks nice would of course be better.

RecipeRow.recipe will no longer be required to be non-null. When it's null, the row will instead display the icon from an arbitrary FactorioObject and a user-specified string, which will be configured with the same sort of UI currently used for ProjectPages. These rows will behave as if they had a real recipe that takes no crafter, fuel, or ingredients, produces no products, and accepts no modules.

Incidentally, this will reduce information loss when loading a project file that contains an unknown recipe. The row itself will still be lost, but any children still will be loaded.