Wisconsin Gov. Scott Walker plans to focus Monday on weakening labor by proposing to abolish unions for federal workers, create a national "right-to-work law" and eliminate the National Labor Relations Board.At a Las Vegas manufacturer, he also plans to call for requiring all unions to hold periodic votes so workers can decide whether they should continue to exist, according to his campaign. He will also cancel President Barack Obama's Labor Day order that federal contractors provide paid sick leave and work to end policies requiring some salaried workers to receive overtime—saying in some cases they should get time off instead."It's...