JShell/Kulla towards JDK9 and Fix Version

[Robert Field]

We believe the core work of JShell is done, that the functionality is 
there and fairly stable, and yes sure there are bugs to fix, but they 
are not too glaring.  What that means is it is time to work towards 
moving JShell into the JDK9 main-line repo!

This also has an effect on what Fix Version we use.  Work that we need 
to do before it goes into JDK9 (e.g., API docs clean-up) or, because of 
timing, we know will go into the Kulla repo should continue to use the 
9-repo-kulla Fix Version.  Everything else, including almost all bug 
reports, should have Fix Version: 9.

-Robert