Review JAXP Java SE 9 API javadocs

This review covers the following items:

(1) Review javadocs to make sure they are current with regard to Java SE 9 APIs
    Adjust contents where necessary.

(2) Add missing package descriptions
     The following packages in java.xml did not have package description:

javax.xml
javax.xml.stream
javax.xml.stream.events
javax.xml.stream.util
org.w3c.dom.bootstrap
org.w3c.dom.events
org.w3c.dom.ls
org.w3c.dom.traversal
org.w3c.dom.views

(3) Convert package description from package.html to package-info.java
    Adjust format where appropriate