RFR 9: 8034906: Fix typos, errors and Javadoc differences in java.time

[roger riggs]

Please review for JDK 9, editorial corrections and cleanup for java.time 
classes.
The grammar has been improved and some redundant @throws NPE clauses 
removed.
Javadoc links have been corrected.  Original patch from Stephen Colebourne,
some additions and corrections by me.

webrev: http://cr.openjdk.java.net/~rriggs/webrev-typos-8034906.patch/

Issue: https://bugs.openjdk.java.net/browse/JDK-8034906

Thanks, Roger