The new arguments greatly simplify adding properties such as alignment
and (HTML) background colors to table cells. For example, to make a
table with 'right alignment for the left-hand column, 'center alignment
for the second column, and 'left alignment for all remaining columns:
(tabular cells
#:sep (hspace 1)
#:column-properties '(right center left))
Also, make `color-property` and `background-color-property` recognized
as table-cell style properties.
Finally, implement horizontal alignment for text rendering.
original commit: 316fc0dbf5e26061245d815c992cc54d9738aa79
0fd78b8ca8