Fix syntax error.
Import 'top', 'center', 'bottom' vertical alignment from xlsx.

And use it in html output.  We still need to handle other vertical
alignment types.
Let's use 'middle' instead of 'center' for vertical alignment.

Stick with CSS's wording when in doubt.
Add output format type 'none' which disables writing output files.

This is useful for benchmarking.
Add xlsx test file for importing 2-variable data table.
Parse and import data tables from xlsx.

Data table not yet stored in the spreadsheet model.
Add test xlsx file for importing single-variable data tables.

Both column and row-oriented tables.
Fix the one-var data tables.

The column and row input cell references were flipped.
Move set_data_table() interface to import_sheet.

It makes more sense to keep it together with the rest of the formula
import methods.
New xlsx test file for importing autofilters.
Remove old debug outputs.
A little cleanup.
Started parsing the autoFilter data. Not finished yet.