Usability improvements to org-lparse-convert and co (First cut)

Usability improvements to org-lparse-convert and co (First cut)

* contrib/lisp/org-lparse.el (org-lparse-and-open)
(org-lparse-register-backend, org-lparse-format-table)
(org-lparse-begin, org-lparse-end): Checkdoc related fixes.
(org-lparse-get-converter): Added
(org-lparse-get-other-backends, org-lparse-all-backends):
Re-implemented. Also improved docstring.
(org-lparse): Make use of improvements in the converter
routines. Improve the following: a) gathering of
target-backend and native-backend args during interactive
calls b) error handling.
(org-lparse-convert): Introduced prefix arg for opening of
converted files. Make use of improvements in the converter
routines. Improve error handling.
(org-lparse-convert-processes): New customizable variable.
(org-lparse-convert-process): Make it customizable. Set
default value to nil.
(org-lparse-convert-capabilities): New customizable variable.
(org-lparse-use-flashy-warning): Fix group and improve docstring.

* contrib/lisp/org-odt.el (org-odt-get): Don't set
CONVERT-METHOD and OTHER-BACKENDS options. Fallback to the
global converter settings for now.
(org-export-odt-preferred-output-format): New variable
(org-export-as-odt-and-open, org-export-as-odt): Use the
afore-mentioned variable.

* contrib/lisp/org-xhtml.el (org-xhtml-get): Don't set
CONVERT-METHOD and OTHER-BACKENDS options. Fallback to the
global converter settings for now.