Mercury News: A Palo Alto start-up with powerful backing on Thursday unveiled an ambitious $1 billion plan to help make the Bay Area the nation’s electric-car capital. Endorsed by all three of the Bay Area’s big city mayors, the plan would provide the re-charging infrastructure that must be in place before most consumers would consider buying or leasing an electric car. Better Place, headed by former high-tech executive Shai Agassi, plans to install about 250,000 charging ports, 200 …