Changes for document Nexus Migration Guide

Because of the bug [[MRELEASE-459>>http://jira.codehaus.org/browse/MRELEASE-459]] of the maven-release-plugin, the ##<releaseProfiles>ow2-release<releaseProfiles>## plugin configuration’s element is not honored if your maven’s release environment has no **active profile** when the release ifis performed. That leads to **missing artifacts** (like javadocs and sources artifacts) in the staging repository.