added files to simplify build

src/Kp2aBusinessLogic/Io/DropboxFileStorageKeysDummy.cs

@@ -0,0 +1,13 @@
+namespace keepass2android.Io
+{
+	public partial class DropboxFileStorage
+	{
+		private const string AppKey = "";
+		private const string AppSecret = "";
+	}
+	public partial class DropboxAppFolderFileStorage
+	{
+		private const string AppKey = "";
+		private const string AppSecret = "";
+	}
+}