Update freemind converter
* lisp/org-macs.el (org-called-interactively-p): New macro.
* lisp/org-freemind.el: No longer require 'rx.
(org-freemind): New customization group, use it for all the variables.
(org-export-as-freemind): Add docstring.
(org-freemind-show): Improve filen naming.
(org-freemind-convert-links-helper): New function.
(org-freemind-bol-helper-base-indent): New variable.
(org-freemind-bol-helper): New function.
(org-freemind-node-css-style): New option.
(org-freemind-node-pattern): New variable.
(org-freemind-from-org-mode): Better docstring.