Main Screen fixes

Added confimation dialogues for deleting parts/products;
Finished implementing Product class methods;
Propogating part modifications to associated products;
Stopped deleting of items if there is an association;

C968Project/Views/AddModifyProductScreen.cs

@@ -12,9 +12,14 @@ namespace C968Project.Views
 {
     public partial class AddModifyProductScreen : Form
     {
-        public AddModifyProductScreen()
+        private ScreenOption screenOption;
+        private Product? _product;
+
+        public AddModifyProductScreen(ScreenOption screenOption, Product? product)
         {
             InitializeComponent();
+            this.screenOption = screenOption;
+            _product = product;
         }
     }
 }