Add first time initialization

Add a initialization algorithm if there is no config file and no environmental variable is given. Especially if there is not Discord token.

• Ask for Discord token
• Create Config struct
• Write created Config as config file
• Continue to run normally

This ensures that valid config file with default options is created.

Also something like --save-config option may be added to save current running config to the config file. May be even overwrite it if it exists.