Add properties to describe failed requests

[ghost]

From @kupsch, regarding p.147, response object:

The response object should have a mechanism to indicate that no response was received from the server. This could happen due to a DNS failure or a connectivity issue such as the server not running or the host or port being inaccessible. Should add a requestFailed and requestFailureReason at a minimum. This is similar to an invocation where process creation failed.

[michaelcfanning]

TC approves this change:

request.noResponseReceived : defaults to false
request.failureReason : of type string

[michaelcfanning]

@lgolding, on further review, I believe Jim had it right to begin with: noResponseReceived belongs on the response object. We should consider renaming 'reasonPhrase' to 'failureReason' to allow it to be used for this case. We should probably discuss in more detail soonest and loop in Jim.

[michaelcfanning]

@lgolding these changes need to go into the schema asap

[ghost]

The current proposal is simply to add webResponse.noResponseReceived. We will overload webResponse.reasonPhrase to hold the error message in this case.