Add support for `@apiNote` and `@implNote` for Java doc plugin

[nobeh]

Java 8 interfaces introduce default methods. The documentation for such methods provides two more extension points for documentation @apiNote and @implNote which are not by default enabled in the Java doc plugin.

References:

• https://bugs.openjdk.java.net/browse/JDK-8008632
• http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-April/016149.html
• http://blog.codefx.org/java/new-javadoc-tags/