Merge English DQGen with Swahili DQGen Lite into multilingual DQGen

[JackMostow]

Current DQGen can only handle English input, because it relies on some English resource, like Google n-grams database, to generate distractors. And we have a Swahili version called “DQGen lite”, so our goal is to combine these two version into one program, which can handle both English and Swahili inputs.