Added fix for #64 to keep building in spite of javadoc errors

There is some debate about switching this to be the default in the Maven Javadoc plugin (https://jira.codehaus.org/browse/MJAVADOC-387).

Since I could not find a solution that would let us enable some of the checks and disable others (for the Mojo classes that fail) I think robot builds should disable JDK8 lint checking for javadoc by default.