Arima/initial

Initial implementation of ARIMA Time Series support, and a few helper BLAS and related attributes.
Five global iterates is going to scale REALLY badly across large systems. Can you help be understand what we are doing here?
I -looks-like the base := stuff is ensuring that accumulation only occurs within a single model ID. If I am reading this correctly - can we not group by model ID and do group iterates (which are much faster)