org-table: Use "ox.el" internally for radio tables

org-table: Use "ox.el" internally for radio tables

* lisp/org-table.el (org-table-clean-before-export, orgtbl-get-fmt,
  orgtbl-apply-fmt, orgtbl-eval-str, orgtbl-format-line,
  orgtbl-format-section): Remove functions.
(org-table-clean-did-remove-column, *orgtbl-table*, *orgtbl-rtn*,
  *orgtbl-hline*, *orgtbl-sep*, *orgtbl-default-fmt*, *orgtbl-fmt*,
  *orgtbl-efmt*, *orgtbl-lfmt*, *orgtbl-llfmt*, *orgtbl-lstart*,
  *orgtbl-llstart*, *orgtbl-lend*, *orgtbl-llend*): Remove variables.

(org-table-export, orgtbl-send-table): Apply function removal.  Do not
set `org-table-last-alignment' and `org-table-last-column-widths'
anymore.
(org-table-to-lisp, orgtbl-send-replace-tbl): Small refactoring.

(org-table--to-generic-table, org-table--to-generic-row,
org-table--to-generic-cell): New functions.
(orgtbl-to-generic): Rewrite function.  Handle :skip and :skipcols
parameters.
(orgtbl-to-latex, orgtbl-to-html, orgtbl-to-texinfo, orgtbl-to-orgtbl,
orgtbl-to-unicode): Use new `orgtbl-to-generic' features.

* testing/lisp/test-org-table.el (test-org-table/to-generic,
  test-org-table/to-latex, test-org-table/to-texinfo,
  test-org-table/to-html, test-org-table/to-unicode,
  test-org-table/send-region): New tests.

* doc/org.texi (Radio tables, A @LaTeX{} example, Translator
  functions): Update documentation.

* etc/ORG-NEWS (argument): Document new features.