TAREK AMARA and ANGUS McDOWALL TUNISIA’S President Kais Saied has indicated he was preparing to change the country's constitution but said he would only do so using existing constitutional means, seven weeks after he seized powers in moves his foes called a coup. The comments represented his clearest statement yet about what he intends to do next, having sworn there was "no going back" to the situation in the North African nation before his intervention on July 25. Speaking live on television in a central Tunis boulevard, Saied said he respected the 2014 democratic constitution but that it was not…