Improved bloom lens effect

The lens effects imager has improved bloom modes that can run in a fraction of a second and produce more interesting bloom effects. The new aperture bloom mode procedurally mimics the bloom defined by a physical camera and you can control the size with bloom_strength, and the shape and number of spikes with aperture_blades and aperture_curvature. The other new mode, shape_file allows you to load a bloom kernel from disk.