updating change log for recent IECoreHoudini commits (in range r4750-4770)
updating change log for recent IECoreHoudini commits (in range r4750-4770)

goddardl/cortex,davidsminor/cortex,hradec/cortex,danieldresser/cortex,davidsminor/cortex,danieldresser/cortex,danieldresser/cortex,hradec/cortex,appleseedhq/cortex,hradec/cortex,danieldresser/cortex,davidsminor/cortex,goddardl/cortex,appleseedhq/cortex,lento/cortex,goddardl/cortex,lento/cortex,davidsminor/cortex,appleseedhq/cortex,lento/cortex