Clarified Yes/No buttons in Merge question dialog

src/Kp2aBusinessLogic/IKp2aApp.cs

@@ -50,6 +50,16 @@ namespace keepass2android
             EventHandler<DialogClickEventArgs> yesHandler, 
             EventHandler<DialogClickEventArgs> noHandler, 
             EventHandler<DialogClickEventArgs> cancelHandler, 
+            Context ctx);
+
+		/// <summary>
+		/// Asks the user the question "messageKey" with the options Yes/No/Cancel, but the yes/no strings can be selected freely, calls the handler corresponding to the answer.
+		/// </summary>
+		void AskYesNoCancel(UiStringKey titleKey, UiStringKey messageKey,
+			UiStringKey yesString, UiStringKey noString,
+			EventHandler<DialogClickEventArgs> yesHandler,
+            EventHandler<DialogClickEventArgs> noHandler,
+            EventHandler<DialogClickEventArgs> cancelHandler,
             Context ctx);
 
 		/// <summary>

src/Kp2aBusinessLogic/UiStringKey.cs

@@ -30,6 +30,10 @@ namespace keepass2android
 		CheckingTargetFileForChanges,
 		TitleSyncQuestion,
 		MessageSyncQuestion,
-		SynchronizingDatabase
+		SynchronizingDatabase,
+		yes,
+		no,
+		YesSynchronize, 
+		NoOverwrite
     }
 }

src/Kp2aBusinessLogic/database/edit/SaveDB.cs

@@ -78,7 +78,9 @@ namespace keepass2android
 					{
 
 						//ask user...
-						_app.AskYesNoCancel(UiStringKey.TitleSyncQuestion, UiStringKey.MessageSyncQuestion,
+						_app.AskYesNoCancel(UiStringKey.TitleSyncQuestion, UiStringKey.MessageSyncQuestion, 
+							UiStringKey.YesSynchronize,
+							UiStringKey.NoOverwrite,
 							//yes = sync
 							(sender, args) =>
 							{