Those of us old enough to remember Thurgood Marshall on the Supreme Court of the United States remember him as a stern, heavy presence. So what a surprise to meet him again in “Marshall” and to find out that, as a young man, he was a very cool guy — fearless and charismatic, and not just brilliant but up for a good time. “Marshall” is a historical drama that will introduce many Americans to the life and career of one of the 20th century’s most important lawyers.