* allow users that have tiki_p_admin_wiki perm to change the wiki authors style for each page,
  * allow admins to choose the position of the bar of actions buttons (save, cancel, preview...) : top (above textarea), bottom, both + factorize code of buttons for preview mode and for normal edit mode,
  * add a feature 'Save Draft' in wiki admin page, to be able to hide the 'Save Draft' button when editing a wiki page,
  * display a message ($date - Version $num of this page has been saved by $user) after a page has been saved,
  * css: by default, put wiki actions buttons on the right when they are above textarea (position = top),
  * in some places, use the new way of handling ':' chars at the end of translated strings