Function addOnError

Adds an error handler to our global error queue. the error handler must be of the format function errorListener(<errorData>) with errorData being of following format:

• errorData.type : "error"
• errorData.status : the error status message
• errorData.serverErrorName : the server error name in case of a server error
• errorData.serverErrorMessage : the server error message in case of a server error
• errorData.source : the issuing source element which triggered the request
• eventData.responseCode: the response code (aka http request response code, 401 etc...)
• eventData.responseText: the request response text
• eventData.responseXML: the request response xml