Support a platform parameter for Qemu

I'm sure we will discover a distribution with a different
naming conventions...

Fix #220

gns3server/handlers/api/qemu_handler.py

@@ -51,9 +51,10 @@ class QEMUHandler:
         qemu = Qemu.instance()
         vm = yield from qemu.create_vm(request.json.pop("name"),
                                        request.match_info["project_id"],
-                                       request.json.get("vm_id"),
-                                       qemu_path=request.json.get("qemu_path"),
-                                       console=request.json.get("console"))
+                                       request.json.pop("vm_id", None),
+                                       qemu_path=request.json.pop("qemu_path", None),
+                                       platform=request.json.pop("platform", None),
+                                       console=request.json.pop("console", None))
 
         for name, value in request.json.items():
             if hasattr(vm, name) and getattr(vm, name) != value: