Adds critter crates

All animals ordered through cargo will arrive in critter crates. These
crates keep themselves warm and filled with oxygen (for a very limited
amount of time). Critter crates can only be unlocked from the outside
and automatically lock when closed. You can *resist* your way out of the
crates. Critter crates are counted as normal crates when sent back.

Adds cat crate (cost: 40 points).

Corgi crate now has a 50-50% chance of either containing a male or
female corgi.

Removes redundant large animal crates.

This update is pug-ready.