Add parameters to customize the output of a Logger.

[jalavosus]

These parameters allow for customizing the output of the logger, such as:

• Showing the timestamp of the log message at all
• Showing a unix timestamp (in seconds or nanoseconds) instead of a stringified timestamp
• Showing a separator between the log level and message
• Customizing the separator between the log level and message
• Colorizing the log message based on its log level.