Freezing update

[Qatavin]

Relating to #477.

While adding heating_energy to entities, I decided to do what I could to add snow as well. Results were mixed. The rules as I understand them say that pointing to Space Age assets is fine so long as they aren't distributed with a mod that doesn't have a Space Age dependency. If you only point to them, you can have only an optional dependency. I'm not sure why even that is needed, but that's what's been said. I could do a lot more if I could modify the graphics and place them in a separate mod (Bob's Space), but it feels to early to do that just for the sake of making snow. The game does apply a tint to frozen entities regardless, and there is a "frozen" icon displayed over them when in alt mode, so it's not like the snow is strictly necessary anyway.

Assembling machines, electronics machines, and chemical plants were easy enough. I did add a few missing secondary_draw_orders. Centrifuges and oil refineries didn't need any updating. Furnaces were the first problem. The old graphics didn't fit the new snow; everything was slightly off. So I replaced the old version of the chemical furnace with one that had the chemical tank on top be its own separate layer. This also allowed me to have the tank appear to be in front of the snow.

Distilleries and compressors/water pumps simply use snow from pipes, and I cut out a section of the machine's graphics to place on top of the snow in order to provide the necessary occlusion. No snow was available to top the machines themselves, though. And I had even less to work with for the electrolysers, which only have pipe_cover snow. Same thing for small storage tanks. All-corner ones also have problems. I tried to get sneaky with them by compounding the two orientations of the vanilla storage tank's snow, but it turns out that the frozen sprites that storage tanks use does not make use of parameters x, y, or position. You can only use whole sprite starting from 0, 0. This one, at least, I'm sure I could perfect fairly easily if I could modify the graphics.

I saw that vanilla stone and steel furnaces do not freeze in the cold, so I decided to extend that to burner and steam assembling machines and steam inserters, to give them a bit of an opportunity to shine. Basic transport belts also share this trait.

For modular roboports, once again, I couldn't find any snow to use on the logistic network interface or the zone expanders. The robochests, though, since their tops are rectangular, I was able to use x and y parameters to cut out a section of the roboport's snow. I did something similar with the charge pads, using the snow from an inserter's base. I configured the heating_energy for the modular roboports such that when you add them up they should be a little less than a whole roboport to make up for their larger footprint, except that robochests have twice the storage space of roboports, so their heating_energy cost is twice as much.

For pipes, I did a little reorganizing. Since there's no possible scenario where all pipes won't be available if Plates is enabled, I combined all of their conditionals into one. Labs were no problem. Greenhouse could use a bit of a touch-up on its pipe connector snow, but it's basically fine too.

Pumpjacks were no issue, as expected. Water pumpjacks, though, needed a bit of an adjustment. There seem to have been some very slight modifications to the baseline pumpjack graphics over the years, but water pumpjacks use an old version that has integrated shadows, which is a problem, since the shadows take on the tint that colors the structure. This isn't particularly noticeable on Nauvis, but it is very noticeable on Aquilo. I haven't replaced it yet, but it probably should be.

Turrets have heating_energy but no snow. I guess you aren't expected to build them, given that there're no enemies on Aquilo.

One final important note: Here, I have all tiers of an entity have the same heating_energy requirement. However, we could make it so higher tiers require less, with a few exceptions like transport belts, which would require a bit more per tier. Just a thought.