Changed the tabbed dialog API to include an epilogue that

Changed the tabbed dialog API to include an epilogue that
can be used to display data common to all tabs, such as submit buttons.
Removed recurring event support from TECH_PREVIEW and moved into the mainline
code.  Event editor tabs for Event/Attendees/Recurrence are now working, even
though the Recurrence tab doesn't yet display an editor, for now it just
displays the raw RRULE data.