Improve error messages

[kbtz]

It is really nice to be able to split the config file but I had to stop using includes because if I have any errors in my configuration it will only show a generic error message that doesn't print the line that caused the error and the line number reported isn't very useful since it's from the config file that is generated after all includes are appended.

It would be a great improvement to have error messages to also print the source line while also taking in consideration if that is coming from a include. Thanks!