Add custom log

[matthis-d]

Add logging in the application to get more details on eventual errors.

[matthis-d]

In application.properties, add this following code:

# Level for loggers on classes inside the root package "netgloo" (and its 
# sub-packages)
# Available levels are: TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF
logging.level.com.matthisd.slacktcl= DEBUG

And in Java code, something like:

  // Define the logger object for this class
  private final Logger log = LoggerFactory.getLogger(this.getClass());