By Mahamat Ramadane N’DJAMENA (Reuters) -About 50 people were killed and nearly 300 injured in violence that broke out in Chad on Thursday as hundreds took to the streets to demand a quicker transition to democratic rule. Prime Minister Saleh Kebzabo, who gave the death toll at a news conference, said the government was still compiling casualties from what he described as an armed insurrection. But human rights groups said that unarmed civilians were massacred as security forces brutally cracked down on demonstrations in the capital, N’Djamena, and several other cities. The vast, military-run …