The reason is that multiple data sets will always be grouped.
If we add null values to fix the grouping issue, we will still have
space between the bars.
Changed the colors of the Deep-/Light Sleep and Activity datasets.
* Deep sleep has been used as basic color,
* Light sleep is a color that is monochromatically analogous
* Activity is a color triadic to the basic one
- supports zooming an panning
- displays labels for all x-values (= time of day)
- fix deep vs. light sleep constants
- increase activity data buffer size for Mi Band