Add support for the session GUID in the UI

The Session GUID will identify active sessions, and is the beginning of
work that will allow for tracking of sessions that have come back alive
after failing or switching transports.

modules/payloads/singles/python/meterpreter_reverse_https.rb

@@ -38,7 +38,8 @@ module MetasploitModule
       url:             generate_callback_url(opts),
       http_user_agent: opts[:user_agent],
       http_proxy_host: opts[:proxy_host],
-      http_proxy_port: opts[:proxy_port]
+      http_proxy_port: opts[:proxy_port],
+      stageless:       true
     })
 
     py_create_exec_stub(met)