Track sleep depth for shorter increments of an hour or so

From Rocky on 2017/09/28 04:01:59 +0000

Before my last update, I used to get sleep depth statistics for naps. (An hour or so.) Don’t anymore. Often I sleep in several shorter periods, so I’m losing sight of how much deep sleep I’m getting.

Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/31655599-track-sleep-depth-for-shorter-increments-of-an-hou