146 photosynthesis

Added photosynthesis, a chloroplast organelle (placed in editor with hotkey P, no GUI button until we get a better GUI), and environmental CO2 emitters.

Also:
-made some changes to the repo structure, including the definitions in assets/ and excluding the new website files.
-cleaned up microbe and organelle creation code, use OrganelleFactory for all your organelle-placement needs.

Will squash commits and merge once approved.
Perhaps just reduce the spawnrate (the 1/20^2) for all our emitters to reduce clutter