Implemented velocity based particles
replaced position offset and position tags in favour of setting
emiter_shape - rectangular that defines the shape of emitter
Refactored particle and emitter class. Values that can vary from particle
to particle now wrapped in approperiate classes
render agnostic - particles doesn't contain ifnormations about how to
render them
added previous render method using bitmap data as debug renderer - needs
to be attached using static function from ParticleSystem class
updating emmiters by delta time provided by hand - gives greater controll
over the simulation
fix for custom timestep