New module for EventSource code.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12760 e27351fd-9f3e-4f54-a53b-843176b1656c
minor


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12761 e27351fd-9f3e-4f54-a53b-843176b1656c