AccountPopover: Close if settings button gets clicked
user-list-entry: Give the settings button some margins
MainWindow: Sort the Accounts by their ID
style.css: Fix hover button padding
AccountCreateWidget: Fix some ordering issues
MainWindow: Set the account popover's header func

We can't use a border-bottom since that would give us a double border at
the bottom of the list.
MainWindow: Don't add the dummy account to the popover