gui: Refactoring Part 1 (#1859)

* gui: Refactoring Part 1

* Fix ProfileDialog.glade path

* Fix Application.Quit assert

* Fix TitleUpdateWindow parent

* Fix TitleUpdate selected item

* Remove extra line in TitleUpdateWindow

* Fix empty assign of Enum.TryParse

* Add Patrons list in the About Window

* update about error messages

Ryujinx/Ui/Widgets/UserError.cs

@@ -0,0 +1,39 @@
+namespace Ryujinx.Ui.Widgets
+{
+    /// <summary>
+    /// Represent a common error that could be reported to the user by the emulator.
+    /// </summary>
+    public enum UserError
+    {
+        /// <summary>
+        /// No error to report.
+        /// </summary>
+        Success = 0x0,
+
+        /// <summary>
+        /// No keys are present.
+        /// </summary>
+        NoKeys = 0x1,
+
+        /// <summary>
+        /// No firmware is installed.
+        /// </summary>
+        NoFirmware = 0x2,
+
+        /// <summary>
+        /// Firmware parsing failed.
+        /// </summary>
+        /// <remarks>Most likely related to keys.</remarks>
+        FirmwareParsingFailed = 0x3,
+
+        /// <summary>
+        /// No application was found at the given path.
+        /// </summary>
+        ApplicationNotFound = 0x4,
+
+        /// <summary>
+        /// An unknown error.
+        /// </summary>
+        Unknown = 0xDEAD
+    }
+}