No roof, no solar power. That has been the dispiriting equation shutting out roughly half of all Americans from plugging into the sun.Subscribe to The Post Most newsletter for the most important and interesting stories from The Washington Post. But signing up for solar soon might be as easy as subscribing to Netflix. Scores of new small solar farms that sell clean, local electricity directly to customers are popping up. The setup, dubbed "community solar," is designed to bring solar power to peo