Add LiipThemeBundle

Re-defined the config / user relation to be OneToOne bidirectionnal.
ConfigType is now a service so I can inject the list of available themes that are also used by LiipThemeBundle

Force sqlite for test
In case of people use a different driver in parameter.yml (yes I do :))

composer.json

@@ -75,6 +75,7 @@
         "tecnick.com/tcpdf": "~6.2",
         "simplepie/simplepie": "~1.3.1",
         "htmlawed/htmlawed": "dev-master",
+        "liip/theme-bundle": "1.1.3",
         "wallabag/PHP-Flash-Messages": "dev-master",
         "wallabag/kriss_php5": "dev-master",
         "wallabag/pagination": "dev-master",