By Sheila Dang and Greg Roumeliotis NEW YORK (Reuters) -Elon Musk has taken ownership of Twitter Inc with brutal efficiency, firing top executives but providing little clarity over how he will achieve the ambitions he has outlined for the influential social media platform. “The bird is freed,” he tweeted after he completed his $44 billion acquisition on Thursday, referencing Twitter’s bird logo in an apparent nod to his desire to see the company have fewer limits on content that can be posted. The CEO of electric car maker Tesla Inc and self-described free speech absolutist has, however, also …