Descrete volume and weights for items

[olanti-p]

Stuff like this

    "id": "blanket",
    "type": "ARMOR",
    "name": { "str": "blanket" },
    "description": "Hiding under here will not protect you from the monsters.",
    "weight": "1123 g",

Is all over the place.

Many items use suspiciously precise numbers for their weights and/or volumes that don't convert nicely into either metric or the other measurement system.

Not only the UI cannot display such precision:

But since we're not pursuing realism, there's also literally zero gameplay value in having a 2002 grams item over a 2000 grams one. On the contrary, round numbers are much easier to calculate in mind if for example the player would want to estimate how much 3 or 4 copies of an item would weight.

Thus, the proposal is to:

1. Choose a discrete value for volumes and weights.
   10 grams / 10 milliliters may be a good starting point, as it the smallest the UI can display.
   Older Cata used 250 milliliters, not sure whether we want to go this far.
2. Update weight and volume in all items with a script
3. Ammo items may need special handling, as their volume is defined per stack but their weight - per unit
4. (Maybe) Add a check for discrete values on item load

[chaosvolt]

Some of these values are for the sake of showing as exactly X pounds, since that's the default weight unit used. Doesn't apply to oddball volume units however, since those are in liters by default.

[scarf005]

since #2510 it's the other way around tho, now kg is the default

[scarf005]

was writing script to find and replace such values to something more sane, e.g 1kg/1250g. also about pounds, should we change it to 450g or 500g?

[chaosvolt]

540 is closer, since that's about 453.592 grams. Round-to-nearest is probably best approach for stuff like that.