Description
This function allows you to iterate through all of the config
names that have values associated with them. Then getConfig()
or getConfigValue() can be used to get the data itself.
This function will continue to return strings until it reaches the
end of the list, at which time undefined is returned.
Returns
A string containing the next name, or
undefined when the end of list is reached or there is an error.
In case of error, the program will croak() with an appriopriate message.