MEXICO CITY (Reuters) -A group protesting the disappearance of 43 students in Mexico in 2014 knocked down a door to the country's presidential palace, video from local television stations showed on Wednesday morning. The protesters rammed down the door using a white pickup truck from Mexico's state electrical company, videos showed, while President Andres Manuel Lopez Obrador was giving his daily morning press conference inside. Police at the scene used tear gas to disperse the group and law enf