Rewrite settings handling to load on startup

Now uses json to store, manually editable

Closes #644

NHSE.WinForms/Subforms/Program/SettingsEditor.cs

@@ -1,22 +1,18 @@
 using System.Windows.Forms;
-using NHSE.WinForms.Properties;
 
 namespace NHSE.WinForms;
 
 public partial class SettingsEditor : Form
 {
-    private readonly Settings obj;
-
     public SettingsEditor()
     {
-        obj = Settings.Default;
         InitializeComponent();
-        PG_Settings.SelectedObject = obj;
+        PG_Settings.SelectedObject = Program.Settings;
     }
 
     private void SettingsEditor_FormClosing(object sender, FormClosingEventArgs e)
     {
-        obj.Save();
+        // Settings are saved when Main form closes
     }
 
     private void SettingsEditor_KeyDown(object sender, KeyEventArgs e)