Adds Hiding and Passtable to smaller simple_animals

This is a re-purposed pull from #1565 with its controversial feature (ventcrawling for simple animals) removed

Now that magic mania is live a lot of people are getting polymorphed and it's more clear then ever that when you're a mouse with a max health of 5 you need SOMETHING going for you.

Hiding is the ability to hide under structures (mainly tables) to avoid detection. Alien larva already have this skill
PASSTABLE is required to get under a lot of those aforementioned structures (mainly tables)

Large animals, like cows, don't get these things.