Switching works, but doesn't do anything nice with session management. Still need to get things wired into posix, and probably rip out the wininet stuff as well given that I probably won't refactor it to support this.
* Transports are now defined by a set of callbacks that are bound to the Remote.
* Transport initialisation and dispatching is seprated.
* The context of the transport should be switchable depending on new transport requirements.
More to do, but it has begun.
