Define and use ShuttleGui::ConnectRoot...

... And corrected improper connections in HistoryWindow and ContrastDialog,
improper because they got called with the wrong this pointer, to
the control instead of the dialog.  But that was harmless anyway because the
handlers did not use this.

src/PluginManager.cpp

@@ -578,10 +578,9 @@ void PluginRegistrationDialog::PopulateOrExchange(ShuttleGui &S)
 
          mEffects = S.Id(ID_List)
             .Style(wxSUNKEN_BORDER | wxLC_REPORT | wxLC_HRULES | wxLC_VRULES )
+            .ConnectRoot(wxEVT_KEY_DOWN,
+                      &PluginRegistrationDialog::OnListChar)
             .AddListControlReportMode({ _("Name"), _("State"), _("Path") });
-         mEffects->Bind(wxEVT_KEY_DOWN,
-                           &PluginRegistrationDialog::OnListChar,
-                           this);
 #if wxUSE_ACCESSIBILITY
          mEffects->SetAccessible(mAx = safenew CheckListAx(mEffects));
 #endif