Changed the pom to a snapshot version, which is what should happen after a release.  Updated plugin versions, which is usually safe.  Added groupIds to most of the plugin declarations, which is best practice.  Upgraded pom to use the latest Maven plugin APIs and real annotations instead of Maven javadoc tags.  Maven 3.x should be widely used now as it's such an easy upgrade, all Maven 3.x versions should run with this POM configuration.  Upgraded BuildMojo.java to use Maven Annotations instead of the older javadoc tags (which negates the need for the javadoc taglets).
Changed the javadoc plugin to not fail on error because Java 8 javadoc tool is so strict.  Reverted back some character changes from entities to original self that was done to keep javadoc happy, not realizing initially the complaining was from Java 8.  Added a bunch of Javadocs to a few classes, there is a lot that doesn't have it, so decided to just leave it with what I added for now, unless javacpp authors don't like them.