RFR: JDK-8186153, , Fix a11y and HTML issues in the java.math, java.text and java.time packages

[Jonathan Gibbons]

Please review the following changes to fix accessibility and HTML issues 
in the
java.math, java.text and java.time packages.

Mostly, it's "more of the same", setting scope=row|col on tables.
One bigger change is in DateTimeFormatter, to change a preformatted ASCII
table into a standard HTML table.

JBS: https://bugs.openjdk.java.net/browse/JDK-8186153
Webrev: http://cr.openjdk.java.net/~jjg/8186153/webrev.00/
API: http://cr.openjdk.java.net/~jjg/8186153/api.00/

-- Jon