* in the JMAP API as well as in several places in the Groupware
framework, use a single jmap.Response[T] object to return the
payload, the language, the session state and the etag/state instead
of individual multi-valued return values
* jmap: add UpdateContactCard and UpdateCalendarEvent funcs
* use JSON marshalling and unmarshalling into a map for toPatch()
implementations
* add updating ContactCards and CalendarEvents to tests
* add deleting ContactCards and CalendarEvents to tests
* make query response totals work when the value is 0
* tests: use CreateContactCard and CreateCalendarEvent funcs to create
objects in tests instead of using a different JMAP stack that works
with untyped maps
