Bulk patch for ORB contribution

This is the (hopefully) last bulk patch for the ORB.

This includes the following elements:

• JUnit tests for "hello world" functionality (client stream-based invocations)
• code to make the JUnit test work.

As such, this is a platform where we can now start doing work in smaller chunks. Up til now "nothing worked" so it was rather difficult to submit individual patches tied to individual Jira issues.

The patch needs the idlj plugin in a version that is not yet in maven repository