Add support for properties org.apache.maven.global-settings and org.apache.maven.user-settings in maven forked processes

In a corporate environnement I define in MAVEN_OPTS the properties org.apache.maven.global-settings and org.apache.maven.user-settings to define custom settings for the user and its environment.

MAVEN_OPTS=-Xss64m -XX:MaxPermSize=256m -Xms64m -Xmx512m -Duser.language=en -Duser.locale=en -Duser.home=E:\Dev\data\settings -Dorg.apache.maven.global-settings
=E:\Dev\data\settings/jtbox-settings.xml -Dorg.apache.maven.user-settings=E:\Dev\data\settings/user-settings.xml

In my customized global settings I define a location for the local repository which isn't the default location.

When I use the shitty plugin it installs the testing version of the plugin in my custom local repository. But When my integration tests are launched, maven uses the default location for the local repository and it doesn't find the testing version of my plugin.