allow AssemblingMachinePrototype.fixed_quality regardless of fixed_recipe

[protocol_1903]

I'd like to be able to make a machine that automatically forces the recipes produced to a specific quality, but not need to specify the recipe for it. I'd also like this functionality to be extended to furnaces such that you can have quality 'upgraders' and 'downgraders'. Tertially, it would be useful to be able to change this target quality at runtime via scripting (like LuaEntity.result_quality, but it doesn't go away between crafts). Along the same lines but being a bit of a stretch, specifying what quality items can be used for such a recipe (say, like how quality filters have > < >= <= = ~= and wildcard) such that you can have machines that force the item to a specific quality but only if it meets a set of criteria.

Any of these features, if implemented, would greatly expand the possibilities of scripted quality. This request is inspired by the current lack of good supported functionality to allow for custom quality implementations, specifically those used by Inverted Quality. The first two requests would greatly simplify part of the runtime scripting for the mod, allowing for larger and less (script) intensive bases. It would also allow for better implementations of the two new features, downgrade ports and meltdown facilities, such that they are more user friendly and much simpler to build and interact with.

[thesixthroc]

+1