Add log verbosity levels

[mayabar]

Define constants for different levels + go over all log messages and decide to which verbosity level it belongs.

Update readme file with level description.

[mayabar]

Log levels:

• Error - use logger.Error
• Info - use logger.Info
• Debug - use logger.V(logging.DEBUG).Info
• Trace - use logger.V(logging.TRACE).Info

Information logged per request should be logged on a trace level
Information logged for every api call should be logged on a trace level