Modify CdfList output format for data records.

Following advice from Michael Liu, make sure that NOVARY record values
are visually distinguished from virtual ones.  At the same time,
improve output format so that record numbers are aligned better.
Type CDF_TIME_TT2000 is now handled almost correctly.

The discrepancy between TT and UTC including leap seconds is correctly
handled, up to 2012.  The only thing that doesn't work is that the
time is formatted wrongly during the leap second - e.g. a
TIME_TT2000 value of 284040066183000000L should be formatted
"2008-12-31T23:59:60.999000000" but is actually formatted
"2009-01-01T00:00:00.999000000".
Nail that pesky leap second.

The formatting now correctly presents TT_TIME2000 times that fall during
a leap second as appearing in the 61st second of the minute in question,
rather than in a duplicate 1st second of the next minute.
Move EpochFormatter from package ..cdf.record to ..cdf.
Leap second bug fixes.

Following detailed comparison with NASA implementation made a couple of
changes.
Add detailed test case for TIME_TT2000 formatting.
Comment out test against apparently broken NASA result
Simplify slightly