Feature/improve localization (#1147)

* use locale to set language header

* rewrite i18n provider and drop dependency

* rename file

* rename CrudMixin to HttpRepo

* refactor: code-cleanup

* add crowdin source

* remove unused translations

* grab translations from dev branch

* add translation support for foods, units, and labels

* remove rich import

frontend/lang/messages/pl-PL.json

@@ -401,11 +401,11 @@
     "shopping-lists": "Lista zakupów"
   },
   "sidebar": {
-    "all-recipes": "All Recipes",
+    "all-recipes": "Wszystkie",
     "categories": "Kategorie",
     "dashboard": "Kokpit",
     "home-page": "Strona główna",
-    "manage-users": "Manage Users",
+    "manage-users": "Zarządzanie",
     "migrations": "Migracje",
     "profile": "Profil",
     "search": "Wyszukaj",
@@ -486,4 +486,4 @@
     "you-are-not-allowed-to-create-a-user": "Nie masz uprawnień do tworzenia użytkowników",
     "you-are-not-allowed-to-delete-this-user": "Nie masz uprawnień do usuwania użytkowników"
   }
-}
+}