Support org-table syntax in tables extension

Emacs org-table uses a `+` instead of a `|` when drawing header dashes. It would be nice if the tables parser would support this syntax.

    | Column A | Column B | Column C |
    |----------+----------+----------|
    | Cell A1  | Cell B1  | Cell C1  |
    | Cell A2  | Cell B2  | Cell C2  |
    | Cell A3  | Cell B3  | Cell C3  |

org-tables will always include `|` on left and right side of table and only the internal `|`'s are replaced with `+`.

Currently the tables extension will detect the table but throw out all columns but the first. This patch will cause simple org-tables to be parsed correctly.