XWIKI-11285: No way to switch back to original language after looking to a translation
* Fixed the display of the languages, to display on top the current language, and in the submenus the other languages of the document, including original language of document + translations
* Fixed the display of the language pretty name, to display the language in the language itself, this way when switching to Chinese and wanting to go back to english, english will be displayed as "English"
XWIKI-11316: No way to access the document currently being exported from the pdf template
* Added a velocity variable in pdf.vm to store the current translated document ($tdoc), this way when $tdoc will be changed by the render function of the pdftemplate properties, this var will still point to the current document being exported.