Updated docs/tmux, docs/emacs and docs/shell

  * emacs/emacs.org: set 'org-link-file-path-type' to "'relative";
  * shell/bash.org: rewrite paragraph for '11context' profile, fix links
    to 'tmux' document;
  * tmux/tmux.org: rewrite some paragraphs, remove old (and now wrong)
    text, update some scripts (simplification), fix links to 'bash.org'.