Deprecated Baggy

- a big message will be displayed to user using the Baggy theme
- switching from Material to Baggy is no more allowed in config (it'll be forced to material)
- the theme label in the config for Baggy is now _Baggy (DEPRECATED)_

src/Wallabag/CoreBundle/Form/Type/ConfigType.php

@@ -24,7 +24,13 @@ class ConfigType extends AbstractType
         $this->themes = array_combine(
             $themes,
             array_map(function ($s) {
-                return ucwords(strtolower(str_replace('-', ' ', $s)));
+                $cleanTheme = ucwords(strtolower(str_replace('-', ' ', $s)));
+
+                if ('Baggy' === $cleanTheme) {
+                    $cleanTheme = 'Baggy (DEPRECATED)';
+                }
+
+                return $cleanTheme;
             }, $themes)
         );