Based on Allen Wittenauer's comments on HADOOP-12557 findbugs report is not needed in the distro.
Let's remove it.
Fix up Hadoop POMs, roll up JARs to latest versions
generateReports property is not applicable for maven-site-plugin:attach-descriptor goal
Build target to generate findbugs html output
Add information in BUILDING.txt about the need for the FINDBUGS_HOME environment variable for docs builds.