treat private, non-anonymous mucs like 1:1 chats notification wise

src/main/java/eu/siacs/conversations/entities/Conversation.java

@@ -519,6 +519,13 @@ public class Conversation extends AbstractEntity implements Blockable {
 		return getContact().getOtrFingerprints().contains(getOtrFingerprint());
 	}
 
+	/**
+	 * short for is Private and Non-anonymous
+	 */
+	public boolean isPnNA() {
+		return mode == MODE_SINGLE || (getMucOptions().membersOnly() && getMucOptions().nonanonymous());
+	}
+
 	public synchronized MucOptions getMucOptions() {
 		if (this.mucOptions == null) {
 			this.mucOptions = new MucOptions(this);

src/main/java/eu/siacs/conversations/services/NotificationService.java

@@ -64,7 +64,7 @@ public class NotificationService {
 		return (message.getStatus() == Message.STATUS_RECEIVED)
 			&& notificationsEnabled()
 			&& !message.getConversation().isMuted()
-			&& (message.getConversation().getMode() == Conversation.MODE_SINGLE
+			&& (message.getConversation().isPnNA()
 					|| conferenceNotificationsEnabled()
 					|| wasHighlightedOrPrivate(message)
 				 );

src/main/res/values/strings.xml

@@ -108,8 +108,8 @@
 	<string name="pref_vibrate_summary">Also vibrate when a new message arrives</string>
 	<string name="pref_sound">Sound</string>
 	<string name="pref_sound_summary">Play ringtone with notification</string>
-	<string name="pref_conference_notifications">Conference notifications</string>
-	<string name="pref_conference_notifications_summary">Always notify when a new conference message arrives instead of only when highlighted</string>
+	<string name="pref_conference_notifications">Notifications in Public Conferences</string>
+	<string name="pref_conference_notifications_summary">Always notify when a message arrives in a public conference instead of only when highlighted</string>
 	<string name="pref_notification_grace_period">Notification grace period</string>
 	<string name="pref_notification_grace_period_summary">Disable notifications for a short time after a carbon copy was received</string>
 	<string name="pref_advanced_options">Advanced Options</string>

src/main/res/xml/preferences.xml

@@ -83,7 +83,7 @@
             android:title="@string/pref_sound" />
 
         <CheckBoxPreference
-            android:defaultValue="true"
+            android:defaultValue="false"
             android:dependency="show_notification"
             android:key="always_notify_in_conference"
             android:summary="@string/pref_conference_notifications_summary"