Fixed an invalid mesh name that was causing crashes.
Crashes fixed related to playing with new and small microbes made in the editor.
Added a Species Registry to load microbe species from XML,
and modified microbe spawning code to use the species data. Some new ai microbe
species have joined the party, and modders can easily make more just by modifying
two files (scripts/microbe_stage/setup.lua for spawning parameters, and
assets/definitions/microbes.xml for the species). OrganelleFactory was also
refactored to make it easier to create new organelles -- one need not edit
OrganelleFactory.makeOrganelle anymore. Fixes #184