Add :unit field to table columns, is applied on new line for table
headers generated using lxTableHeader.
Added error checking for lxValue in the case where we did not find
the key given.

Add scale option for .lx Columns, divides that column by specified
amount.

Changed internal getYAML() helper to not use glob, and always check
for files not being in sitemap.

If :unit is in table header, add parentheses around it.