Updated docs/emacs

  * emacs.org: simplified settings (several 'setq' lines merged into
    one), set desired Dired+ view, use 'zathura' to view PDF files;
  * updated (tangled) TOP/emacs.d files:
    - bookmark+-us.el;
    - dired+-us.el;
    - org-us.el.

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