Update site for Maven 3.1.x
Update plugin to new LTS version of Jenkins.

One test had to be rewritten as hudson.util.RunList now is not an
ArrayList anymore but an AbstractList.
Update some dependencies needed with newer base version.
Do not warn when a SCM does not support getAffectedFiles.
grey.png now empty.png for jobs with no builds.
Relative paths must not start with a slash.