App & channel notification settings updates

- change 'block all' to an on/off switch bar
- update channel list summary text when notifications are
toggled on/off on app settings page
- Add 'off state' text
- change style of foot items
- change 'importance' from a dropdown to its own page

Bug: 37538972
Bug: 37479730
Fixes: 37541624
Fixes: 37549732
Test: manual

Change-Id: I0e5cc66ba539ce2b76b4ad6541bf6bfb5b58c373

src/com/android/settings/search/SearchIndexableResources.java

@@ -65,6 +65,7 @@ import com.android.settings.location.LocationSettings;
 import com.android.settings.location.ScanningSettings;
 import com.android.settings.network.NetworkDashboardFragment;
 import com.android.settings.nfc.PaymentSettings;
+import com.android.settings.notification.ChannelImportanceSettings;
 import com.android.settings.notification.ConfigureNotificationSettings;
 import com.android.settings.notification.SoundSettings;
 import com.android.settings.notification.ZenModePrioritySettings;
@@ -179,6 +180,8 @@ public final class SearchIndexableResources {
                 R.drawable.ic_settings_accessibility);
         addIndex(AccessibilityShortcutPreferenceFragment.class, NO_DATA_RES_ID,
                 R.drawable.ic_settings_accessibility);
+        addIndex(ChannelImportanceSettings.class, NO_DATA_RES_ID,
+                R.drawable.ic_settings_notifications);
     }
 
     private SearchIndexableResources() {