Mark CEF ISO_TIME columns as time-like.

Add the "time.epoch" UCD to ISO_TIME columns.  This can be picked up
by applications (TOPCAT) to understand the column as an ISO-8601 time.
You could argue it should be in the units, but that's not really right either.
CdfList now reports more variable metadata.

DataTypes now know their own name, and Variables can report on information
like shape, r/z type and record/dimension variances.
Record definite array shapes for parameters in CEF.
Correct misconception about row/column majority.

The indices are always written in the same order: A[2,3] is always
the element in row 2 and column 3, it's just the storage order
that differs.
Provide datatype-specific formatting of variable values.

The main reason this is required is for date-type values.
This is implemented for CDF_EPOCH data type, but not yet for
CDF_EPOCH16 and CDF_TT_TIME_2000.  A utility class
EpochFormatter is provided for DIY formatting.
Report offsets/lengths as hexadecimal in CdfDump.
CdfList cosmetics.

Write a blank line before each variable description.
Look absolutely everywhere for VXRs.

You need to walk both VXR subtrees and the linked list of VXRs headed
in each VXR.
Fix CDF string array reading bug.