Modify default error handlers

Default error handlers was introduced here: #23 (closed)

For example

{
    "id": "CommonErrorReporter",
    "task_type": "graph",
    "task_identifier": "CommonErrorReporter.json",
    "label": "CommonErrorReporter",
    "default_error_node": true
}

In the previous definition default_error_node could also be a dictionary with link attributes. In the new definitions we will do this:

{
    "id": "CommonErrorReporter",
    "task_type": "graph",
    "task_identifier": "CommonErrorReporter.json",
    "label": "CommonErrorReporter",
    "default_error_node": true,
    "default_error_attributes": {"map_all_data": True, "data_mapping":{}}  # the default when missing
}

Ping @koumouts