This gives renderTable a little more customisation. Before any of the
commits of this PR, render would just receive a string to display in
each cell. After the second commit of this PR it would also receive a
width of the string (in place of stripping ANSI sequences and then
calculating the width). After this commit, it now also takes an
alignment, so you can make cells left or right aligned. The function
render calls renderTable with appropriate options to give the same
behaviour as before. Also, previously render would always put a border
around the table. We would take this output, and would sometimes strip
the border by dropping the first and last rows, and first and last
characters of every row. I've just added an option to control whether
to put the border in, so we can just not add it in the first place,
rather than stripping it later. Note that this is again just defining
helper functions; this extra power is not yet used anywhere.
