observatory herald (#30)

* WIP: initial commit for observatory herald

* Plugin error handling refactor

* make error window non-modal

* tidy up plugin error handling

* first pass for basic herald functionality

* corrections for linux env

* Use FNV hash directly instead of managing through dictionary/index file

* resolve audio queuing issue, switch to personal NetCoreAudio fork

* merge cleanup

* add enable setting, populate defaults

* framework xml doc update

* Adjust settings, add style selection, replace locale with demonym in dropdown list.

* Test is position is on screen before saving/loading.

* use a default that's actually in the list

ObservatoryCore/ErrorReporter.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Observatory
+{
+    public static class ErrorReporter
+    {
+        public static void ShowErrorPopup(string title, string message)
+        {
+            if (Avalonia.Application.Current.ApplicationLifetime is Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime desktop)
+            {
+                var errorMessage = MessageBox.Avalonia.MessageBoxManager
+                .GetMessageBoxStandardWindow(new MessageBox.Avalonia.DTO.MessageBoxStandardParams
+                {
+                    ContentTitle = title,
+                    ContentMessage = message,
+                    Topmost = true
+                });
+                errorMessage.Show();
+            }
+        }
+    }
+}