* Change the start date of the parent event to the current date
for tests that with events that recur forever.
* Limit query results to 100 for events that recur forever that can
generate more than 100 event records.
Issues fixed:
* Additional rule validations.
* Rewrote recurrence logic.
* Additional unit tests, especially from the examples in the RFC.
* The date format "YmdThis" results into an incorrect date for the
"UNTIL" parameter. The literal "T" should be escaped, and a literal
"Z" is also needed at the end of the format string to indicate UTC.
* Implemented handling of negative modifier values for BYxxx rules.
* Implemented handling of BYWEEKNO, BYYEARDAY, BYSETPOS, BYHOUR,
BYMINUTE, BYSECOND rules.
Jun Pataleta