internal/stats: add edm/edmx detectors

Add single-instance edm/edmx breakout detectors. These algorithms are
described in the paper:

This implementation was compared against an open-source R
implementation, and yielded the same breakouts for a wide range of data
from cmd/bent.

Change-Id: I088e37e6444e3c9d3275a15d04b5cecf6e1d2fe9
TryBot-Result: Go Bot <>
Trust: Jeremy Faller <>
Run-TryBot: Jeremy Faller <>
Reviewed-by: David Chase <>
5 files changed