RFR JDK-8209109: [TEST] rewrite com/sun/jdi shell tests to java version - step1

[Alex Menkov]

Hi all,

Please review a fix for
https://bugs.openjdk.java.net/browse/JDK-8209109
webrev:
http://cr.openjdk.java.net/~amenkov/sh2java/webrev/

This is a first step in shell to java conversion of com/sun/jdi tests
The fix introduces base classes to work with jdb and converts couple tests.

--alex