have --check report result using exit code

If any unexpected jarfiles are found, it will exit
with a nonzero exit code.  This allows it to be
used from a script (e.g., the release script)
to check that no unexpected jarfiles exist.
better handling of python ImportErrors

Also, ensure that a CompilationResult always has a list of
CompilerDiagnostics.
Build model classes with debug info
use the standalone version of Jython