Added static method GetSection and test.
Made ClientConfiguration.UriString a ConfigurationProperty and added JetBrainsAnnotations to the project.
Changed som class names and descided that the reference to HttpMessageHandler is acceptable - interface wrapping feels like test-centric overkill. For now.

Added equality comparer (abstract) and get hash code to the XmlResponseBase.

Added ContractError class.
ClientConfiguration stuff.
Unit tests to that drives new features.