RFR [14/java.xml] 8231083: Clarify SAX documentation

[Joe Wang]

Please review a follow-up doc clarification patch after 8230814 [1]. In 
this patch, the statement with a reference to the SAX project is moved 
to an apiNote in package/sub-package description to reflect the fact 
that it is a historical note in nature. The license related text that 
appears in the class description of every SAX class is removed and 
consolidated with the existing text in the license header.

JBS: https://bugs.openjdk.java.net/browse/JDK-8231083
webrev: http://cr.openjdk.java.net/~joehw/jdk14/8231083/webrev/index.html

[1] https://bugs.openjdk.java.net/browse/JDK-8230814

Thanks,
Joe