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

composer.lock

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "25b03b05eeff545aa68314784c949834",
+    "content-hash": "a2a09b8c7c80d9411cb07680b46952a5",
     "packages": [
         {
             "name": "babdev/pagerfanta-bundle",
@@ -5780,74 +5780,6 @@
             },
             "time": "2019-04-17T17:58:44+00:00"
         },
-        {
-            "name": "liip/theme-bundle",
-            "version": "1.7.0",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/liip/LiipThemeBundle.git",
-                "reference": "362394821ff8dcc90b06272e289e7dafe4dab52a"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/liip/LiipThemeBundle/zipball/362394821ff8dcc90b06272e289e7dafe4dab52a",
-                "reference": "362394821ff8dcc90b06272e289e7dafe4dab52a",
-                "shasum": ""
-            },
-            "require": {
-                "php": "^7.0",
-                "psr/log": "~1.0",
-                "symfony/finder": "^3.0|^4.0",
-                "symfony/framework-bundle": "^3.0|^4.0",
-                "symfony/templating": "^3.0|^4.0",
-                "symfony/twig-bundle": "^3.0|^4.0",
-                "twig/twig": "^1.34|^2.4"
-            },
-            "conflict": {
-                "sebastian/comparator": "1.2.3"
-            },
-            "require-dev": {
-                "phpunit/phpunit": "^6.0",
-                "symfony/console": "^3.0|^4.0",
-                "symfony/expression-language": "^3.0|^4.0"
-            },
-            "type": "symfony-bundle",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "1.4-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Liip\\ThemeBundle\\": ""
-                }
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Community contributions",
-                    "homepage": "https://github.com/liip/LiipThemeBundle/contributors"
-                },
-                {
-                    "name": "Liip AG",
-                    "homepage": "http://www.liip.ch/"
-                }
-            ],
-            "description": "Provides theming support for #Symfony2 Bundles",
-            "keywords": [
-                "themes",
-                "theming"
-            ],
-            "support": {
-                "issues": "https://github.com/liip/LiipThemeBundle/issues",
-                "source": "https://github.com/liip/LiipThemeBundle/tree/1.7.0"
-            },
-            "abandoned": "sylius/theme-bundle",
-            "time": "2019-06-19T12:53:08+00:00"
-        },
         {
             "name": "masterminds/html5",
             "version": "2.7.6",