Hunger change

Changes the hunger system in various ways:
* New hunger hud icons that makes people aware of their nutrition level at all time, not just when they're starving or fat. 
![](http://i58.tinypic.com/f9dpxl.png)
* Food w/o sugar can be loaded into the Chef's compartment of snack vending machines by anyone using a tray, and can be bought like regular snacks.
* Fixing a bug where you can't load omelette on a tray.
* Rearranging datum/reagents and splitting the huge Chemistry-Reagents.dm into smaller files, all "good" medical reagents are under datum/reagent/medicine/ and all food&drink reagents are under datum/reagent/consumable. Removed some unnecessary code in Chemistry-Reagents.dm .
* Adding a pizza crate to cargo orders and creating children to /obj/item/pizzabox to contain each type of pizza. (taken from baystation12)
* Adding two new var for mobs "satiety" and "metabolism_efficiency".
* Adding one new reagent "vitamin". It raises satiety. It has the same probability as nutriment to heal brute damage but also burn damage. It barely affects your nutrition. If you manage to get max satiety and stop eating vitamin, you will keep all satiety related bonuses for up to 16mins.
* Changing the "sugar" reagent. Its nutrition boost depends on how fed you are. If well fed, you get no boost. The more hungry you are, the bigger the boost. Sugar intake is metabolized pretty fast but it lowers your satiety. 
* Growns and cooked food are given vitamin while junk food are all given sugar. 
* Slightly lowering snack food amounts in snack vending machines.
* Slightly lowering nutriment amount in junk food (compensated by adding sugar to them)
* Adding another nutrition level between the current 'full' and 'fat' level (max nutrition before going into fat territory is now 550 instead of 450).

* metabolism_efficiency affects the metabolization speed of healing and damaging reagents (like toxins), the radiation effect from reagents that deals radiation and the efficiency of bodytemp stabilization via calory use. Higher metabolism_efficiency means medicine reagents stay longer in your body and the opposite for damaging reagents, less radiation from radium or uranium, faster stabilization of bodytemperature. metabolism_effiency gets higher when fed and positively satiated and lower when starving or fat. The metabolism_efficiency can have three values currently: 0.8 , 1 (default) and 1.25 .

* satiety handles hunger rate, if negative your nutrition is drained five times faster than default (does not affect nutrition changes due to movements). A high positive satiety while being decently fed boosts the metabolism efficiency. Vitamin intake raises satiety, sugar intake lowers it. satiety naturally changes toward 0 over time. When satiety is greatly negative you cannot eat more sugary food (unless you are starving) and must wait for satiety to go up again. A positive satiety lowers your chance to catch and spread viruses(the higher the satiety the better). satiety is bound between -200 and 600. If you binge eat sugar and get -200 satiety, you will lose 100 nutrition points over the next 6min30 (instead of 20pts).

* If you eat/drink too much sugary food (junk food from snack vending machine mostly), you won't be able to eat/drink more sugary food and will have to wait a bit unless you're starving. Example: you reach this point after eating one and a half 4noraisin. The waiting time cannot be higher than 2mins.

* Adding vitamin reagents to most grown and cooked food.
* Adding or increasing sugar amounts in junk food.


What this means:
* The different foods are now balanced, the more easily acquired the food, the more drawbacks it has:
Easily acquired junk food gives a fast and significant nutrition boost but its sugar means getting hungry again sooner and prevents easily reaching the top nutrition and satiety levels.
Donkpocket are junk food unless it is microwaved then you won't be hungry again fast but no satiety boost. (so miners can use hot donkpocket and not be fucked by the change )
Chef recipes boost satiety and nutrition quickly and the more complex the recipe the bigger the boost.
Most growns from botany boost satiety and nutrition but less than chef food unless high potency. 
Easily acquired drinks generally give a decent but slow nutrition boost , no satiety change. (exception for hot coco that's closer to junk food) 
Dry ramen is similar to drinks, but hot ramen (dry ramen+water) gives a higher nutrition boost.
You can order a costly pizza crate for a big nutrition and satiety boost.
Syndi-cake are still the same.
You won't starve even if there's no chef or botanist.

* Players are incentivized to get better food
* Poisoning the chef's food undetected is easier by placing it in snack machines and people will eat those more often than junk food.




It is probably worth making the nutrition levels defines, just for code readability and future maintenance / tweaking of levels.