Support multi-line cell content with word-wrapping

[jwoffindin]

Why:

• It is not currently possible to provide multi-line content for cells as the newlines characters in cell text are output verbatim resulting in corrupted text.
• When wrapping text within cells words are unnecessarily broken across cell boundaries.

This change addresses the need by:

• Add support for word-based wrapping (rather than current character based approach). A "word" is a contiguous sequence of non-whitespace characters. Default to
• Add support for newlines in cell text which result in new cell rows.