added login logout button for news, home and study view
optionsbutton ref#204
buttons iphone high res
Merge branch 'master' into login-logout-button
refs 204
refs #204
Merge branch 'login-logout-button' of https://github.com/University-of-Potsdam-MM/UP.App into login-logout-button
added login/logout-button and username closes #204
fixed merge conflicts
Merge pull request #208 from University-of-Potsdam-MM/login-logout-button

Login logout button closes #204