Adding initialization-on-demand idiom and noninstantiable class instead of interface constant idiom

Sonar quality bugfix and minor refactor

Sonar bug fixes using Yoda condition in equals expression when comparing String literal with String object.
Using try-with-resources if we use Scanner to close the underlying stream is a good practice to handle resources.
Minimal refactor.

Sonar bug fixes using Yoda condition in equals expression when comparing String literal with String object.
Using try-with-resources if we use Scanner to close the underlying stream is a good practice to handle resources.
Minimal refactor.

Module pattern #62

Issue #450. First commit. Queue Based Load Leveling

Add hexagonal architecture presentation

Object Mother pattern #498