Allow to set username
Resolve problems described in #3 (comment 369168637) and add a dialog to set the username. Allow to use the default of "user" easily for casual users who don't care and want to go through the installation faster.
Resolve problems described in #3 (comment 369168637) and add a dialog to set the username. Allow to use the default of "user" easily for casual users who don't care and want to go through the installation faster.