Make Cactus issue a warning if one of the cactus-related jar files it requires
is already in the original war to cactify.
It is important, because conflicts in version may result in unexpected errors like:
Exception starting filter filterredirector
java.lang.ExceptionInInitializerError
For a case details look at
http://jira.codehaus.org/secure/ViewIssue.jspa?key=MAVEN-884