admin is for wifi / esp settings
user is for printer settings
admin and user ID can be defined in config.h
[ESP555]<admin password> allows to reset user password to default one
Separate M20 command from file listing to give time to get the complete
file list before sending the list
Change SDK function system_get_time and wifi_get_opmode to use wrapper
ones and avoid to include user_interface.h if not necessary
