Add sequence metrics to TemporalMemoryInspectMixin

Fixes https://github.com/numenta/nupic/issues/1329.
Builds on https://github.com/numenta/nupic/pull/1338.

@subutai 
I wonder if we could use the name "correctlyPredictedCells" rather than "predictedActiveCells"?  Might be a bit clearer?