Qual: Spelling of admin code. (#27412)

# Qual: Fix spelling of admin code.

Mostly changes in the comments.
Some french text was modified to not trigger a bad spelling.

htdocs/admin/contract.php has a change to $langs->trans(Activated)
which probably fixes a bug.

htdocs/admin/system/xcache.php used ->trans(Recommanded)
but the proper key is ->trans(Recommended).

htdocs/admin/reception_setup.php

@@ -378,7 +378,7 @@ foreach ($dirmodels as $reldir) {
 									print "</td>";
 								}
 
-								// Defaut
+								// Default
 								print '<td class="center">';
 								if ($conf->global->RECEPTION_ADDON_PDF == $name) {
 									print img_picto($langs->trans("Default"), 'on');