This creates a new `Fog::Core::Connection` class that wraps around HTTP
connections/requests but does not presume SAX parsing of the API response.
A new `Fog::XML::SAXParserConnection` is available which implements the
original behaviour with a clearer interface.
`Fog::Connection` subclasses `SAXParserConnection` to be backwards
compatible.
Further testing and deprecation warnings are needed.
Since mock testing occurs at a higher level the changed code is not
exercised by the tests and I do not have access to an XML based API to
debug quickly with.
