RFR: JDK-8196736: Refactor HelpWriter and properties

[Jonathan Gibbons]

Please review a very simple renaming/refactoring of the code and 
properties used to generate the Help page, as a precursor to updating 
the content.

This step does not change the relevant content of the generated page at all.
JBS: https://bugs.openjdk.java.net/browse/JDK-8196736
Webrev: http://cr.openjdk.java.net/~jjg/8196736/webrev.00/

-- Jon