Update clippercms.com and forums URLs in version.inc and help lang files

Change CMS_DOMAIN form clippercms.org to clippercms.com so links to subdirectories work.
Update language files' Help message element to point to correct URL for current forum.
German left as it is, pointing to clippercms.de, though that redirects to clippercms.com;
Czech updated to English forum instead of MODX Czech boards
Portuguese removed references to Portuguese-language boards

NB Hebrew has no relevant entry
Chinese, Japanese & Persian not updated.