Internationalization (German) of the mobile app. (#246)

* Add i18n framework to mobile app and write simple translation generator

* Replace all texts in login_form with i18n keys

* Localization of sharing section

* Localization of asset viewer section

* Use JSON as base translation format

* Add check for missing/unused translation keys

* Add localizely

* Remove i18n directory in favour of localizely

* Backup Translation

* More translations

* Translate home page

* Translation of search page

* Translate new server version announcement

* Reformat code

* Fix typo in german translation

* Update englisch translations

* Change translation keys to match dart filenames

* Add /api to translated endpoint_urls

* Update localizely.yml

* Add languages to ios plist

* Remove unused keys

* Added script to check outdated key in other translations

* Add download key to localizely.yml

Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/pubspec.lock

@@ -253,6 +253,20 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.6"
+  easy_localization:
+    dependency: "direct main"
+    description:
+      name: easy_localization
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "3.0.1"
+  easy_logger:
+    dependency: transitive
+    description:
+      name: easy_logger
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.0.2"
   equatable:
     dependency: "direct main"
     description:
@@ -335,6 +349,11 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.1"
+  flutter_localizations:
+    dependency: transitive
+    description: flutter
+    source: sdk
+    version: "0.0.0"
   flutter_map:
     dependency: "direct main"
     description:
@@ -842,6 +861,62 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.27.3"
+  shared_preferences:
+    dependency: transitive
+    description:
+      name: shared_preferences
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.15"
+  shared_preferences_android:
+    dependency: transitive
+    description:
+      name: shared_preferences_android
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.12"
+  shared_preferences_ios:
+    dependency: transitive
+    description:
+      name: shared_preferences_ios
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.1"
+  shared_preferences_linux:
+    dependency: transitive
+    description:
+      name: shared_preferences_linux
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.1"
+  shared_preferences_macos:
+    dependency: transitive
+    description:
+      name: shared_preferences_macos
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.4"
+  shared_preferences_platform_interface:
+    dependency: transitive
+    description:
+      name: shared_preferences_platform_interface
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
+  shared_preferences_web:
+    dependency: transitive
+    description:
+      name: shared_preferences_web
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.4"
+  shared_preferences_windows:
+    dependency: transitive
+    description:
+      name: shared_preferences_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.1"
   shelf:
     dependency: transitive
     description: