Updated docs/emacs

  * emacs.org:
    - added option to show column number, `column-number-mode';
    - added more templates for cdlatex, mainly to insert environments in
      math mode, reformat code;
  * (TOP)/emacs.d
    - emacs: updated, tangled from Org document;
    - cdlatex-us.el: updated, tangled from Org document.

Signed-off-by: Vladimir Lomov <lomov.vl@gmail.com>