Cleanup exception handling when converting CLR to node

The change set fixes an node crash issues documented in https://github.com/tjanczuk/edge/issues/39

The fix doesn't catch the exception anymore when converting the CLR data to node. It is now handled on the calling side. It does:

- when the data is converted as the result from the original edge call then the exception is passed as the error object into the callback
- when the data is converted as a callback from CLR -> node and an exception occurs the exception is only set as an exception into the CLR Task. There is no 'active' JS function we could pass the result to.