Use impsort-maven-plugin to automaticall check java imports

[sbernard31]

Currently eclipse configuration allow to clean this automatically.

But for external contribution, often this is not done.

impsort-maven-plugin can be used to check this but not support automatic wildcard * import like eclipse. (see revelc/impsort-maven-plugin#21)

Wildcard import are also considered as bad practice. (see https://checkstyle.org/config_imports.html)

So maybe is to :

• change eclipse configuration to not allow it.
• add checkstyle to check this is not used

Note that if contributor which does not use eclipse should be able to sort import with :

mvn impsort:sort

[sbernard31]

So maybe is to :

• change eclipse configuration to not allow it.
• add checkstyle to check this is not used

Done in last commit.