javadoc plug-in should be more explicit

Normally, yetus treats build failures as a "show the whole log" situation. In the case of Javadoc and projects with thousands and thousands of warnings (e.g., Hadoop), the errors that caused the javadoc failure get completely missed. Committers treat these errors as just a temporary failure since they can't find the fault.

In the case of javadoc, we should specifically do two failure checks:
1) Normal build failure output
2) Check for an '[ERROR] ... error: ... ' string and print that output into a separate log.