TimeSeriesInterp:  increase unit test strictness

- typo:  forgot a 0 in an error bound.
TimeSeriesInterp:  add LALREA8SequenceInterp object

- and turn LALREA8LTimeSeriesInterp into a thin wrapper around it.  besides
  making the code more modular and re-usable, this affects a tiny (~1%)
  performance improvement due to a reduction in the number of pointer
  indirections needed.