allow a request to be processed in a job

Now we allow a request to be passed into a job queue,
and after the job finishes the request is passed into
a controller again. In order to achieve this we have
a requests queue in System, when we put a request
to the job this Request structure is preserved in the
queue and for a new request a new Request is added to
the queue.

while here:
- remove App::Lock()/Unlock(), use scoped locking
- fix: Plugin now has a Call method which takes ModelConnector
  and a logger (used in multithreaded environment)
- BaseThread has a main_model_connector pointer
  to the main (from the main thread) model connector
- the FastCGI structure fcgi_request moved from App to Request
- some methods for handling requests moved from App to Request
- small refactoring in main.cpp
- add Http class (a http client)

winixd/core/sessionmanager.h

@@ -5,7 +5,7 @@
  */
 
 /* 
- * Copyright (c) 2008-2019, Tomasz Sowa
+ * Copyright (c) 2008-2022, Tomasz Sowa
  * All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without
@@ -43,7 +43,6 @@
 #include "config.h"
 #include "request.h"
 #include "lastcontainer.h"
-#include "system.h"
 #include "synchro.h"
 #include "basethread.h"
 #include "sessionidmanager.h"