Allow adjustment of heart rate measurement frequency

From Christopher Barraud (grum) on 2017/04/11 14:13:40 +0000

Currently killing my smartwatch battery. Allowing us to change the number of times it polls per hour would help.

Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/18905224-allow-adjustment-of-heart-rate-measurement-frequen