Make it possible to show config file settings

[Sopor]

Now when it is possible to use a config file it would be nice if it was possible to list the config file (if there is one) so it will be easier to view the settings. This will also be possible to use when users create issues. This will also verify that the config file is in the right path if someone have issues with it.
svtplay-dl --show-config and it you want to view a config file with another name than default
svtplay-dl --show-config configfile.