Solar power's growth has become unstoppable for all the right reasons.It's been a tough past few days for First Solar (FSLR 2.25%) shareholders. And understandably so. Investors suspect pro-oil President-elect Donald Trump could also prove unsupportive of renewable energy. Iin fact, most clean energy stocks are down since his Nov. 5 election on this very worry. First Solar has been no exception to the industrywide sell-off.This weakness, however, is also a buying opportunity for anyone interested in owning ...