Convert default properties to non-camelCase
Make has-flower and can-seed default plant props

Flowerbox models now changed so that we only plant non-seeding plants
Build plant flowering and seeding directly into step function

Taking most of this directly from Java
Throw error is try to get nonexistant prop; make isDead a simple prop

Since we're getting everything based on strings, it's easy for an author
to mistype a property and not know about it.

Agents being dead is an engine-level concern, and doesn't need to be in
the agent's properties list (which is for phenotype, breeding, etc.)
Make more properties species-level props

Agent properties should just be for props that change within a species,
props is "is annual" should be at the species level.

This will improve efficiency because these props won't need to be
copied to offspring, and lets us set model-level differences (like
changing a plant to not be able to seed) just once, instead of
in each addOrganism button as we were doing.