This is the first step in getting ConnectionFileDescriptor ported to Windows. It implements a connection against a disk file for windows. This supports connection strings of the form file://PATH which are currently supported only on posix platforms in ConnectionFileDescriptor.
This change depends on D5548, and cannot be submitted until after D5548 goes through.
+jim and greg for taking a look at the changes I've made to Core/Connection and API/SBCommunication, and +reid and david in case anyone wants to look at the details of how I've implemented this on Windows.