Vevent and Recur

The purpose of the following is to define the cardinality of members of
vevent and recur.  All params and named complex values for each member can
appear 0 or 1 times, so we don't have to worry about duplicate names there.

************
vevent
************
  =============
  0-1 
  =============
  "CLASS"         param ":" text
  "CREATED"       param ":" date-time
  "DESCRIPTION"   param ":" text
  "DTSTART"       param ":" dtstval
  "GEO"           param ":" geovalue
  "LAST-MODIFIED" param ":" date-time
  "LOCATION       param ":" text
  "ORGANIZER"     param ":" cal-address
  "PRIORITY"      param ":" privalue
  "DTSTAMP"       param ":" date-time
  "SEQUENCE"      param ":" integer
  "STATUS"        param ":" statvalue
  "SUMMARY"       param ":" text
  "TRANSP"        param ":" transvalue
  "UID"           param ":" text
  "URL"           param ":" uri
  "RECURRENCE-ID" param ":" ridval
  =============
  One the other
  =============
  "DTEND"         param ":" dtendval
  "DURATION"      param ":" dur-value
  =============
  0 or more
  =============
  "ATTACH"         param ":" uri
  "ATTENDEE"       param ":" cal-address
  "CATEGORIES"     param ":" text *("," text)
  "COMMENT"        param ":" text
  "CONTACT"        param ":" text
  "EXDATE"         param ":" date-time/date*(","date-time/date)
  "EXRULE"         param ":" recur
  "REQUEST-STATUS" param ":" 1*DIGIT *("." 1*DIGIT) ";" text [";" text]
  "RELATED-TO"     param ":" text
  "RESOURCES"      param ":" text *("," text)
  "RDATE"          param ":" date-time/date/period *(","
date-time/date/period)
  "RRULE"          param ":" recur CRLF

************
recur
************
  "FREQ"= freq
    =============
    One the other
    =============
    ";" "UNTIL" "=" enddate
    ";" "COUNT" "=" 1*DIGIT
    =============
    0-1
    =============
    ";" "INTERVAL" "=" 1*DIGIT
    ";" "BYSECOND" "=" byseclist
    ";" "BYMINUTE" "=" byminlist
    ";" "BYHOUR" "=" byhrlist
    ";" "BYDAY" "=" bywdaylist
    ";" "BYMONTHDAY" "=" bymodaylist
    ";" "BYYEARDAY" "=" byyrdaylist
    ";" "BYWEEKNO" "=" bywknolist
    ";" "BYMONTH" "=" bymolist
    ";" "BYSETPOS" "=" bysplist
    ";" "WKST" "=" weekday