Set default button on all dialogs. Fixes lp:665703

* Set default button on all dialogs that do not already have a defined
  default button.  The only exception is the EESchema net list dialog
  which needs converted over to wxFormBuilder and due to it's design makes
  setting the default button in any tab other than the default tab
  problematic.
* Fix escape key dialog handling bug in EESchema print post script
  dialog.

gerbview/dialogs/dialog_print_using_printer.cpp

@@ -118,6 +118,8 @@ DIALOG_PRINT_USING_PRINTER::DIALOG_PRINT_USING_PRINTER( GERBVIEW_FRAME* parent )
     {
         GetSizer()->SetSizeHints( this );
     }
+
+    m_buttonPrint->SetDefault();
 }