Merge "Add new strings for b/63109928" into oc-mr1-dev

    <!-- [CHAR LIMIT=100] Notification Importance: high importance level description -->

    <string name="notification_importance_high">Make sound and pop on screen</string>

    <!-- [CHAR LIMIT=100] Notification Importance: high importance level description,

     when the user has picked high importance but disabled sound for it -->

    <string name="notification_importance_high_silent">Pop on screen</string>

    <!-- Importance title strings for the Importance page. Also the first part of the importance

     summary on the channel page-->