Adjusted the colors a bit to
1. match material colors
2. have a visible distinction between primary_dark and primarydark_dark
3. match the color used by the action bar and side drawer in dark theme
Also define them in the attrs xml file and do some grouping in the colors xml.
It might be we don't need them at all, but for the time being let's keep them around.
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.
mueller-ma