Checking in the profiler classes separately as I work
around some commit issue with RenderManager.  Actually 
calling of these hooks will follow immediately.
Added hooks for detailed performance profiling.
Implementors can provide their own AppProfiler
implementation to collect and/or visualize timing
stats however they want, even at the viewport level
if they choose.
A basic profiler implementation will be following
shortly that does simple update vs render frame
timings.