Attempting to load an invalid config file will wipe the existing config, leaving the user with an empty config.
This change adds a check when an invalid file is loaded, and asks the user if the invalid config file should be overwritten.
If the user chooses `yes`, then the default config is loaded instead, and the existing config will be overwritten with it.
If the user chooses `no`, then the program exits.
Note this is intended only for the "interactive" mode (the only one existing right now). If and when we go forward with the suggestion in from issue #88, there should be no prompt, just an error message on stderr.
joce
Brandon Lee Camilleri
ImVexed