Drop opinionated settings for PWA

* Base URLs are set to / in PWA's default settings anyway
  * With https://github.com/silviolleite/django-pwa/pull/32 merged, the defaults will
    work under all circumstances without changing settings
* l10n/i18n assumptions should not be made. PWA will see another MR to enabled
  it to use the language settings used in Django

Closes #140.

aleksis/core/settings.py

@@ -389,9 +389,7 @@ PWA_APP_DESCRIPTION = "AlekSIS – The free school information system"  # dbsett
 PWA_APP_THEME_COLOR = lazy_config("COLOUR_PRIMARY")
 PWA_APP_BACKGROUND_COLOR = "#ffffff"
 PWA_APP_DISPLAY = "standalone"
-PWA_APP_SCOPE = "/"
 PWA_APP_ORIENTATION = "any"
-PWA_APP_START_URL = "/"
 PWA_APP_ICONS = [  # three icons to upload dbsettings
     {"src": STATIC_URL + "/icons/android_192.png", "sizes": "192x192"},
     {"src": STATIC_URL + "/icons/android_512.png", "sizes": "512x512"},
@@ -408,9 +406,7 @@ PWA_APP_SPLASH_SCREEN = [
         "media": "(device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2)",
     }
 ]
-PWA_APP_DIR = "ltr"
 PWA_SERVICE_WORKER_PATH = os.path.join(STATIC_ROOT, "js", "serviceworker.js")
-# PWA_APP_LANG = 'de-DE'
 
 CKEDITOR_CONFIGS = {
     'default': {