Add sortpom-maven-plugin to ensure pom.xml files are well formatted.

[sbernard31]

sortpom-maven-plugin allow to check if pom.xml file are well formatted using :

mvn com.github.ekryd.sortpom:sortpom-maven-plugin:verify -PallPom

pom.xml files can be formatted with :

mvn com.github.ekryd.sortpom:sortpom-maven-plugin:sort -PallPom

This validation will be automatically done during build, when mvn clean install is called.

All those will be automatically check on new PR using github actions. Errors will be reported like that : sbernard31#14