Former President Barack Obama paid glowing tribute to predecessors George W. Bush and Bill Clinton and even their spouses in a public post Thursday — while leaving Joe and Jill Biden in the relative dust. Obama’s conspicuous separation of Bush and Clinton — two former presidents who he battled against politically in 2008 — from the Bidens in his appreciation post for attending the opening of his Barack Obama Presidential Center earlier in the day raised eyebrows. “To George and Laura, Bill and