Added package-info for the "org.netbeans.gradle.project.api.entry" package.
Added package-info for the "org.netbeans.gradle.project.api.event" package.
Added package-info for the "org.netbeans.gradle.project.api.nodes" package.
Added package-info for the "org.netbeans.gradle.project.api.task" package.
Fixed javadoc errors.