Order-independent Unfold

The big new feature for this release is order-independent Unfolding. This makes it possible to assemble records from all over the file into single rows.

The documentation for Fold and Unfold has also been improved with several detailed examples.

Fold and Unfold fixes

Fix several more bugs in the Fold and Unfold code:

• Isolate the Fold internal buffer from downstream modifications (like Drop)
• Handle ragged/incomplete records in Unfold

Fold and Unfold fixed fields

Fix a bug where the fixed (not folded) fields were not being copied.

Markdown support

Added support for reading and writing Markdown tables. An example is in the examples directory and can be demonstrated with

python3 convert.py -i md -o csv < table.md | less

The reverse process can be used with Write to generate Markdown tables from another format. Note that formatting is preserved but may need quoting.