Add sequence metrics to TemporalMemoryInspectMixin

Fixes https://github.com/numenta/nupic/issues/1329.
Builds on https://github.com/numenta/nupic/pull/1338.

@subutai 
Yes, I think this should be in Connections.  Logically it makes more sense, and I could see it being useful to other classes (e.g. a classifier).