Improve search to look for items inside ItemGroup

Added a new overloaded version that works on a project.

Updated CoreEnvironmentContributor accordingly.

Avoid deprecated junit.framework.Assert, use org.junit.Assert instead

Add tests for Project class

Add tests for Node class

This reverts commit 1a6f3dfa.
forgot to add this file

Conflicts:
	changelog.html

The code is smart enough to compute a minimum set of builds to remove to
restore order consistency.

Fix javadoc warnings in hudson.model.Queue