By Alasdair Pal and Uditha Jayasinghe COLOMBO (Reuters) -Protesters and a key trade group in Sri Lanka called for a new government to take control of the crisis-hit country on Tuesday as the president called for calm a day after clashes killed eight people, pushing his brother to quit as prime minister. Sri Lanka has been suffering its worst economic crisis in history, with a severe shortage of foreign exchange stalling the essential of imports, including drugs and fuel. For months, its tottering economy has been largely supported by India, which has provided assistance of more than $3.5 billi…