RFR:JDK-8148950 :Enhance ChronoField Javadoc

[nadeesh tv]

Hi all,

Please see the doc changes 
http://cr.openjdk.java.net/~ntv/8148950/webrev.00/
Bug ID https://bugs.openjdk.java.net/browse/JDK-8148950
--
Thanks and Regards,
Nadeesh TV