nexus-2.11.x switch to jruby-1.7.17

and use IsolatedScriptingContainer with its new OSGi support. which also
reduces the start up of the ScriptingContainer significantly.

please review and have a look at the startup time of ScriptingContainer
IIUC this change doesn't add huge number of imports for org.jruby.embed classes so I think use of * here is not warranted.  Please add direct imports.