Currently we get the heart rate when synchronizing activity data
(i.e. not live) and we write it to the activity database so that we
can show a nice graph. The value is currently always 0 though,
because we can't enable recording hr, yet.
First comes the pie chart (details) now, the the bar chart (overview)
Maybe we should do this differently in the sleep and week-steps
fragments, but for a start, and having it consistently, this is how it is.
