Austin (AFP) – Tesla welcomed throngs of electric car lovers to Texas Thursday for a huge party inaugurating a “gigafactory” the size of 100 professional soccer fields. Online buzz has swelled ever since Tesla’s colorful but controversial founder and chief executive Elon Musk tweeted word of the event, with reports of perhaps as many as 15,000 guests taking part in the official plant opening in the state capital Austin. Tesla owners posted plans for cross country road trips, while others urged the uninvited to just show up and find a way inside. As Thursday arrived, Musk tweeted images and vi…