Add logging levels to the Contribution Guide

[osopardo1]

As stated in #288 , we can have 4 levels of Logging information:

• WARN level is supposed to be critical and actionable. If the user sees a WARN, then something bad happened and it might require user intervention.
• INFO level provides information about the execution, but not necessarily actionable and it avoids being verbose. It is not uncommon to see INFO level on in production, so it is expected to be lightweight with respect to the volume of messages generated.
• DEBUG provides debug level info when debugging the code. It can be verbose as it is not expected to be on in production.
• TRACE provides further detail to DEBUG on execution paths, and in particular, it indicates critical the methods that been executed.

We should add this information with more detailed cases in our Contribution Guide.