XWIKI-9176: New XWiki Syntax Guide

 * move table with from inline stlye to css and reduce width to 99%
 * keep language in left navigation (first attempt)
XWIKI-9176: New XWiki Syntax Guide

 * update content to latest version of the previous pages
 * add separate "other syntaxes" page
 * new section "advanced"
 * language now also preserved in syntext switch