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/system.h

@@ -5,7 +5,7 @@
  */
 
 /* 
- * Copyright (c) 2010-2018, Tomasz Sowa
+ * Copyright (c) 2010-2022, Tomasz Sowa
  * All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without
@@ -108,6 +108,9 @@ public:
 	// when winix starts
 	TimeZones time_zones;
 
+	// list of requests, if a request is to be continued in a job then it is preserved in the req_tab
+	// and a new Request is inserted for the next incoming request
+	std::list<Request> req_tab;
 
 	using WinixModelDeprecated::get_model_connector;
 
@@ -221,6 +224,7 @@ public:
 
 	void CreateItemLink(const Item & item, std::wstring & link, bool clear_str = true);
 
+	void DeleteOldRequests(bool leave_one_object = false);
 
 private: