WIP: further wizard improvements

• for keyboard layout setup, parse layout files, write /etc/default/keyboard (re #1 )
• write keyboard layout into wayfire and sway skel files (re #1 )
• make password setting code less hacky by use of crypt(3) API and usermod --password (might deprecate #10 ?)
• write desktop and username choice to /etc/ly/save (re #5 )