Handle deserializing null values to defaults in C#
Handle deserializing null values to defaults in C#

Resolves an issue where the Docker daemon might not send an actual value
that can be deserialized into the strongly typed C# model. In go values
like this are given the default value of the type itself but it does not
cause a failure in deserialization.

Resolves: #61

Signed-off-by: Justin Terry <f0c38945ef01caad6a7c3d4b90a29703264b34a4@microsoft.com>

ahmetalpbalkan/Docker.DotNet,jterry75/Docker.DotNet,jterry75/Docker.DotNet