RFR 8081638: JShell tool: Improve completion for static import

[ShinyaYoshida]

Hi Jan,
Please review this patch:

webrev:
http://cr.openjdk.java.net/~shinyafox/kulla/8081638/webrev.00/

bugs:
https://bugs.openjdk.java.net/browse/JDK-8081638

Regards,
shinyafox(Shinya Yoshida)