Migrate to Oreo and drop support for APIs < 16

Summary:
- Add a foreground notification to the background service
- Add channel to notifications.
- Remove unneeded permission
- Remove legacy ciphers now that we don't support API<16

Reviewers: #kde_connect

Subscribers: mtijink, nicolasfella, albertvaka, apol, kdeconnect, #kde_connect

Tags: #kde_connect

Differential Revision: https://phabricator.kde.org/D12881

res/values/strings.xml

@@ -246,5 +246,6 @@
     <string name="dark_theme">Dark theme</string>
     <string name="notification_channel_default">Other notifications</string>
     <string name="notification_channel_persistent">Persistent indicator</string>
+    <string name="notification_channel_media_control">Media control</string>
 
 </resources>

src/org/kde/kdeconnect/Helpers/NotificationHelper.java

@@ -12,6 +12,7 @@ public class NotificationHelper {
     public static class Channels {
         public final static String PERSISTENT = "persistent";
         public final static String DEFAULT = "default";
+        public final static String MEDIA_CONTROL = "media_control";
     }
 
     public static void notifyCompat(NotificationManager notificationManager, int notificationId, Notification notification) {
@@ -40,6 +41,12 @@ public class NotificationHelper {
 
         NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
 
+        manager.createNotificationChannel(new NotificationChannel(
+                Channels.PERSISTENT,
+                context.getString(R.string.notification_channel_persistent),
+                NotificationManager.IMPORTANCE_DEFAULT)
+        );
+
         manager.createNotificationChannel(new NotificationChannel(
                 Channels.DEFAULT,
                 context.getString(R.string.notification_channel_default),
@@ -47,9 +54,9 @@ public class NotificationHelper {
         );
 
         manager.createNotificationChannel(new NotificationChannel(
-                Channels.PERSISTENT,
+                Channels.MEDIA_CONTROL,
-                context.getString(R.string.notification_channel_persistent),
+                context.getString(R.string.notification_channel_media_control),
-                NotificationManager.IMPORTANCE_DEFAULT)
+                NotificationManager.IMPORTANCE_LOW)
         );
 
     }

src/org/kde/kdeconnect/Plugins/MprisPlugin/MprisMediaSession.java

@@ -308,7 +308,7 @@ public class MprisMediaSession implements SharedPreferences.OnSharedPreferenceCh
 
             final NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
 
-            NotificationCompat.Builder notification = new NotificationCompat.Builder(context, NotificationHelper.Channels.DEFAULT);
+            NotificationCompat.Builder notification = new NotificationCompat.Builder(context, NotificationHelper.Channels.MEDIA_CONTROL);
 
             notification
                     .setAutoCancel(false)