Add support for adding custom data at the top level of the json request (Thanks to Alan Robson for contributing - source: https://groups.google.com/forum/#!msg/jsonrpclib/U1f-aQ-8F6E/E29j77N2BqAJ)
Updated version number
Add data value in JSON RPC error response, only if it has been returned by the server
Merged with feature-add_custom_data & feature-add_custom_data