POM cleanup + fix license in .bat scripts

In this PR : 

 * Remove maven-jar-plugin config in `gatling-app` module : unnecessary, since scripts call the class directly
 * Remove `<name>...</name>` tags : name defaults to artifactId
 * Change maven-license-plugin exclusion pattern to ignore a test resource in charts, suppressing a warning
 * Fix license in `.bat` script, not properly overwritten when license changed