Added GTA V folder check to main entry point in Program.cs, improved folder selection dialog

- Added bool app setting for remember GTA folder (vs. prompt every start)
 - Added checkbox to folder selection dialog for remember GTA folder
 - Changed folder selection dialog to fixed dialog window border
 - Set default Enter/Esc buttons on folder selection dialog

ExploreForm.cs

@@ -59,7 +59,9 @@ namespace CodeWalker
 
             InitFileTypes();
 
-            /*if (!EnsureGTAFolder())*/
+            // This is probably not necessary now that the GTA folder is checked 
+            // in the Program.cs when the game is initiated, but we will leave it 
+            // here for now to make sure 
             if(!GTAFolder.UpdateGTAFolder(true))
             {
                 Close();