Add create-server acceptance test and support code

This check-in is not complete; it will break acceptance tests.  The
problem is that I cannot run the test in full-quiet mode yet; I need to
support listing of images and flavors before I can do that.  That will
allow the acceptance test to choose a server flavor and OS image
appropriate for the acceptance test.
diff --git a/interfaces.go b/interfaces.go
index 16c0589..538743f 100644
--- a/interfaces.go
+++ b/interfaces.go
@@ -20,4 +20,5 @@
 type CloudServersProvider interface {
 	ListServers() ([]Server, error)
 	ServerById(id string) (*Server, error)
+	CreateServer(ns NewServer) (*NewServer, error)
 }