Checkstyle

[plozanol]

As a developer I want to apply the latest official checkstyle xml found in the repo:
https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml

Acceptance

• save the file at the project
• apply the needed config to maven pom.xml, to add a lifecycle stage to allow checking
• all warnings checkstyle warnings will be forced to be errors
• to accelerate development, devs should install the same checkstyle rules, and the checkstyle plugin at their IDE : https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml