GREG-188: Doing some changes to make the header look nicer on mobile screens

I did some changes to the header to try to make it look nicer on mobile screens: I removed the user name from the header if the screen is small. I changed to and emblem and text for UiB when the screen size is small, for UiO the logo is smaller so it still looks OK on smaller screens. I removed the logout icon if the screen is small.