EXDATE master ticket: time zones, durations, etc.

[rianjs]

This ticket combines part of #239 and all of #140.

EXDATEs fold improperly

If you add a second EXDATE to a collection, this is the output:

EXDATE;TZID=UTC:20170404T123000
EXDATE;TZID=UTC:20170403T123000

It should be:

EXDATE;TZID=UTC:20170404T123000,20170403T123000

Unit test:

[Test]
public void ExDateFold_Tests()
{
    var start = DateTime.Now.AddYears(-1);
    var end = start.AddHours(1);
    var rrule = new RecurrencePattern(FrequencyType.Daily) { Until = start.AddYears(2) };
    var e = new Event
    {
        DtStart = new CalDateTime(start),
        DtEnd = new CalDateTime(end),
        RecurrenceRules = new List<IRecurrencePattern> { rrule }
    };

    var firstExclusion = new CalDateTime(start.AddDays(4));
    e.ExceptionDates = new List<IPeriodList> { new PeriodList { new Period(firstExclusion) } };
    var serialized = SerializeToString(e);
    Assert.AreEqual(1, Regex.Matches(serialized, "EXDATE:").Count);

    var secondExclusion = new CalDateTime(start.AddDays(5));
    e.ExceptionDates.Add(new PeriodList { new Period(secondExclusion) });
    serialized = SerializeToString(e);
    Assert.AreEqual(1, Regex.Matches(serialized, "EXDATE:").Count);
}

Specifying a CalDateTime with a TzId should include the TzId as part of serialization ( #239 )

Unit test:

[Test]
public void ExDateTimeZone_Tests()
{
    const string tzid = "Europe/Stockholm";
    var later = _now.AddHours(1);

    //Repeat daily for 10 days
    var rrule = new RecurrencePattern(FrequencyType.Daily, 1) { Count = 10 };

    var e = new Event
    {
        DtStart = new CalDateTime(_now, tzid),
        DtEnd = new CalDateTime(later, tzid),
        RecurrenceRules = new List<IRecurrencePattern> { rrule },
    };

    var exceptionDateList = new PeriodList();
    exceptionDateList.TzId = tzid;
    exceptionDateList.Add(new Period(new CalDateTime(_now.AddDays(1), tzid)));
    e.ExceptionDates.Add(exceptionDateList);

    var serialized = SerializeToString(e);
    const string expected = "EXDATE;TZID=Europe/Stockholm:";
    Assert.AreEqual(1, Regex.Matches(serialized, expected).Count);
}

[rianjs]

So EXDATEs fold properly, and always did. I was creating new PeriodLists underneath (which is allowed). So that wasn't actually a bug. Oh well.

Part 2 is fixed.

[rianjs]

It might help if I connect de-serialization to the TZID, too.