[fix] Revert Debian icon, tu Tux

[enh] New version 1.6.6.
[enh] Add 'Démo menu'

cesiumDownloads.php

@@ -18,9 +18,9 @@ $cesiumDownloads =
 		'extra' => ''
 	], 
 	'debian' => [
-		'title' => 'Debian (et dérivés)', 
+		'title' => 'Debian, Ubuntu (et dérivés)',
 		'url' => sprintf('https://github.com/duniter/cesium/releases/download/v%s/cesium-desktop-v%s-linux-x64.deb', $cesiumVersions['linux'], $cesiumVersions['linux']), 
-		'img' => 'debian.svg', 
+		'img' => 'tux.svg',
 		'desc' => _('Paquet .deb pour Debian ou Ubuntu'), 
 		'extra' => _('En cas de problème&nbsp;:') . '<br /><code>sudo apt-get install -y libgconf-2-4</code>'
 	],

cesiumVersions.php

 <?php
 
 $cesiumVersions = [
-	   'home' => '1.6.5', 
-	'android' => '1.6.5', 
-	  'linux' => '1.6.5', 
+	   'home' => '1.6.6',
+	'android' => '1.6.6',
+	  'linux' => '1.6.1',
 	'windows' => '1.3.11', 
-	'firefox' => '1.6.5', 
+	'firefox' => '1.6.6',
 	    'mac' => '1.3.11', 
-	    'web' => '1.6.5', 
+	    'web' => '1.6.6',
 	
 ];
 	   

head.php

@@ -82,6 +82,10 @@ $bodyIds = !isset($bodyIds) ? '' : $bodyIds;
 							'uri' => dgettext('menu', '/telechargement'), 
 							'label' => dgettext('menu', 'Télécharger')
 						],
+						[
+							'uri' => 'https://demo.cesium.app',
+							'label' => dgettext('menu', 'Démo')
+						],
 						[
 							'uri' => dgettext('menu', '/tutoriel-cesium') . '/', 
 							'label' => dgettext('menu', 'Tutoriel')