Arima/initial

Initial implementation of ARIMA Time Series support, and a few helper BLAS and related attributes.
That was the idea. Now if you have very few model IDs (<< number of nodes) then it will result in skew.
IMO there are some 'questions' we need to ask oursevles - do we intend to support the case where all the data for a single model_id cannot fit on a single node. If the answer is 'yes' then I think we are going to need some cleverness.