add test_group_sharees.py


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@13768 e27351fd-9f3e-4f54-a53b-843176b1656c
Tweak plotting of readStats.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@13769 e27351fd-9f3e-4f54-a53b-843176b1656c