[IO-424] Javadoc fixes, mostly to appease 1.8.0. Attempt to appease Javadoc 1.8.0 but getting "[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:javadoc (default-cli) on project commons-io: An error has occurred in JavaDocs report generation:
[ERROR] Exit code: 1 - javadoc: warning - Error fetching URL: http://download.oracle.com/javase/6/docs/api
[ERROR] javadoc: warning - Error fetching URL: http://download.oracle.com/javaee/6/api"

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/io/trunk@1563233 13f79535-47bb-0310-9956-ffa450edef68