Make Transformer take a RewritePolicy

so that it can pass it to the SandboxAdapter.
Also:
- add RewritePolicy.BlindPolicy, which always returns the same result
- add 2 static instances of BlindPolicy: ALWAYS_INTERCEP and
  NEVER_INTERCEPT
- add an option to the test code to use the NEVER_INTERCEPT policy

Now we have a way to test if not intercepting a constructor call causes
operand stack corruption. As I expected, it does.