Please Review: refactor of Chronology class

[roger riggs]

Hi,

The java.time.chrono.Chronology should be split into an interface for 
Chronology
and an AbstractChronology class that is the base for implementing a 
Chronology.

A number of static methods on the java.time.chrono.Chronology class are
inherited by subclasses but can be incorrectly understood to be instance 
methods.
The methods 'from(Temporal)', of(String)', 'ofLocale(Locale)', and
'getAvailableChronologies()' all have the same static inheritance problem.
They are intended as methods returning a Chronology but in the context
of a specific Chronology, for example JapaneseChronology, can be confused
with methods that return a JapaneseDate.

Please Review:

webrev:
http://cr.openjdk.java.net/~rriggs/webrev-chrono-interface-8025719/

javadoc:
http://cr.openjdk.java.net/~rriggs/javadoc-chrono-interface-8025719/

[1] https://bugs.openjdk.java.net/browse/JDK-8025719