Factor out a GL_ARRAY_BUFFER model to use with emitters
Refactor emitter to use ArrayModel. Relies on a nasty nasty hack. Part of a larger refactor.
Change particle instantiation to use an instance variable rather than a factory method.
Initialise emitter from the constructor. More hacky nonsense that ill get rid of soon.
Introduce technique classes for billboard and bullet emitters. More horrific nonsense that is necessary to break up the refactor into chunks.
Make emitters use techniques and model instance system.