Remove LiipThemeBundle

As baggy theme was removed and material is the only remaining theme, we don't need a theme switched anymore.
So:
- move all `*.twig` files from the material theme folder to the root
- remove useless translations

app/config/config.yml

@@ -171,16 +171,6 @@ nelmio_cors:
             max_age: 3600
             hosts: ['^api\.']
 
-liip_theme:
-    load_controllers: false
-    themes:
-        - material
-    autodetect_theme: Wallabag\CoreBundle\Helper\DetectActiveTheme
-
-    path_patterns:
-        bundle_resource:
-            - "%%bundle_path%%/Resources/views/themes/%%current_theme%%/%%template%%"
-
 fos_user:
     db_driver: orm
     firewall_name: secured_area

app/config/services.yml

@@ -17,7 +17,6 @@ services:
             $defaultLocale: '%kernel.default_locale%'
             $wallabagUrl: '%domain_name%'
             $tablePrefix: "%database_table_prefix%"
-            $defaultTheme: '%wallabag_core.theme%'
             $encryptionKeyPath: "%wallabag_core.site_credentials.encryption_key_path%"
             $fetchingErrorMessageTitle: "%wallabag_core.fetching_error_message_title%"
             $fetchingErrorMessage: '%wallabag_core.fetching_error_message%'
@@ -31,7 +30,6 @@ services:
             $senderName: "%scheb_two_factor.email.sender_name%"
             $storeArticleHeaders: '@=service(''craue_config'').get(''store_article_headers'')'
             $supportUrl: '@=service(''craue_config'').get(''wallabag_support_url'')'
-            $themes: '%liip_theme.themes%'
 
     Wallabag\AnnotationBundle\:
         resource: '../../src/Wallabag/AnnotationBundle/*'
@@ -71,9 +69,6 @@ services:
     Lexik\Bundle\FormFilterBundle\Filter\FilterBuilderUpdaterInterface:
         alias: lexik_form_filter.query_builder_updater
 
-    Liip\ThemeBundle\ActiveTheme:
-        alias: liip_theme.active_theme
-
     Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Google\GoogleAuthenticatorInterface:
         alias: scheb_two_factor.security.google_authenticator
 
@@ -210,7 +205,6 @@ services:
 
     Wallabag\UserBundle\EventListener\CreateConfigListener:
         arguments:
-            $theme: "%wallabag_core.theme%"
             $itemsOnPage: "%wallabag_core.items_on_page%"
             $feedLimit: "%wallabag_core.feed_limit%"
             $language: "%wallabag_core.language%"

app/config/wallabag.yml

@@ -24,7 +24,6 @@ wallabag_core:
         cs: 'Čeština'
         el: 'Ελληνικά'
     items_on_page: 12
-    theme: material
     language: '%locale%'
     rss_limit: 50
     reading_speed: 200