* csv-mode.el: Use lexical-binding. Remove redundant :group args.
(csv-separators): Add TAB to the default.
(csv-invisibility-default): Change default to t.
(csv-separator-face): Inherit from escape-glyph. Remove variable.
(csv-mode-line-format): Remove trailing "--". Move next to line-number.
(csv-interactive-args): Use use-region-p.
(csv--column-widths): New function, extracted from csv-align-fields.
(csv-align-fields): Use it. Use whole buffer by default.
Use :align-to and text-properties when possible.
(csv-unalign-fields): Also remove properties.
(csv-mode): Truncate lines.