Improve testing of xml elements by using xmlElementMatch.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12050 e27351fd-9f3e-4f54-a53b-843176b1656c
Check point. Implemented "external" classes that can proxy various apis through the conduit to get results
from another pod.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12051 e27351fd-9f3e-4f54-a53b-843176b1656c
fix GroupCacher.groupsToRefresh() + minor cleaning


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12052 e27351fd-9f3e-4f54-a53b-843176b1656c