[Jtx Board] Adapt to new immutable ical4j.x PropertyList scheme#440

rfc2822 merged 3 commits into

mainbitfireAT/synctools:mainfrom

407-http-415-when-uploading-jtx-board-task-calendar-object-may-only-have-components-with-the-same-uidbitfireAT/synctools:407-http-415-when-uploading-jtx-board-task-calendar-object-may-only-have-components-with-the-same-uidCopy head branch name to clipboard