column: add --table-empty-lines

column: add --table-empty-lines

The option allows to add empty line to the table. The default behavior
is to ignore empty lines at all.

echo -e "A\nAA\nAAA\n\nAAAA" | ./column --table
A
AA
AAA
AAAA

$ echo -e "A\nAA\nAAA\n\nAAAA" | ./column --table --table-empty-lines
A
AA
AAA

AAAA

Addresses: https://github.com/karelzak/util-linux/issues/593
Signed-off-by: Karel Zak <kzak@redhat.com>