Added new sprites for random objects for everything in random/clothing,
/food, /loot, /medical, and /misc.
Also got distracted and changed how the corn oil/cooking oil tank looks
and how much reagent it holds. Now looks like the rest of the reagent
tanks and holds the same amount of liquid, 1000u.
* Added power cores, a type of large battery cell that get used by
exosuits. The nuclear and phoron variants are self-charging.
* Combat mechs now start with nuclear power cores, allowing them to
sustain themselves indefinitely, so long as they stay out of the action
for a bit.
* Removed basic power cells from the mechfab, replaced with the mech
powercores.
* Mech cell statuses now instantly update as soon as the cell charges or
discharges.
* Added a stack of 10 uranium to the machinist's workshop, which can
print two nuclear power cores.
