Parsing negotiation response should not fail for missing properties

[moozzyk]

Running the client against an ancient (1.x) server fails with an exception reading "not a number" and not giving any clue as to what failed and why. This happens because in the 1.2 protocol the negotiation response did not have the TransportConnectTimeout property but the code parsing negotiation response expects all properties it reads to be present. We should ignore missing properties and allow the client to fail when checking the version of the protocol since it would give the user clear reason why the client cannot connect to the server.

Also see: https://blog.3d-logic.com/2015/05/20/signalr-native-client/#comment-18681