Preserving cause on rethrown exceptions

[rPraml]

We had an issue, that we loose the java stack trace, when we catch the error in javascript and rethrow it.

try {
  // call java code
 someJavaObject.doSomething();
} catch (e) {
 // do some error handling and rethrow the error
 throw e;
}

In this case, you will get a JavaScriptException with only the message containing of the exception, that is thrown by someJavaObject.doSomething();
(So you might get a NPE, but you have no idea, which line of code caused the exception)

In this PR, we try to set the currently processing exception/NativeError and setting it as cause of the JavaScriptException.

Roland

[rbri]

LGTM - great improvement.

[rbri]

@gbrail @p-bakker can i merge this?

[rbri]

@rPraml thanks for this