Foreground/background network stats pie chart.

Load foreground/background network stats, showing combined in chart
series, and also separated in pie chart.  Padding to match spec,
updated action bar tabs, and limit width for wide devices.  Also
clear UI options for requesting fragments.  Move to action bar
overflow menu instead of custom icon.  Show detail chart data outside
current inspection range.

Bug: 5106163, 5143670, 5163064, 5162671, 5148713, 5129036, 5096626
Change-Id: I548fef209e1f714f70ee6bf7098dbdb881692df4