Improvement: Only show relevant push notification settings

[FelberMartin]

Problem Description

In Android, we displayed all notification settings as toggles in the notifications settings page, even if some of them should not support push notifications, or are not available to the user because of their role (eg students could change settings for "Instructor Notifications")

This PR closes #439

Changes

• Hide notifications that are not relevant for push notifications (ssh, vcs-token, data-export)
• Hide notifications based on the user's authorities
• Extracted localization into PushNotificationLocalization
• Extracted filtering logic into new PushNotificationSettingUtil
• Added tests

Steps for testing

1. Log in as a student and see that only relevant notification settings are shown
2. Log in as a tutor/editor/instructor and see that the authority based notifications are shown