The Tesla Gigafactory is shown under construction outside Reno, Nevada May 9, 2015. Picture taken May 9, 2015 CARSON CITY — The first building phase of Tesla’s massive battery factory being constructed in Northern Nevada is nearly complete, a legislative panel was told Thursday. But the 900,000-square-foot building represents just 14 percent of the total size of the factory at build-out. “That building will…