Washington Post: With the controversy over the Keystone XL pipeline extension surfacing yet again - opponents will hold a rally Wednesday night in San Francisco`s Pacific Heights neighborhood, outside a fundraiser President Obama is headlining--we thought we`d clarify a few points about the contentious project. (For more details, read Steven Mufson`s new e-book, "Keystone XL: Down the Line.") What is the Keystone XL pipeline? The Keystone XL pipeline extension is a 1,700-mile project that would transport 800,000...