logic: Added update checker connecting to online API

* connects to https://www.sourcetrail.com/api/v1/versions/latest
* sends information about OS, platform, license type, current version and a unique user token
* Automatic update check is enabled via Startscreen and performed once every 24 hours on window focus
* Update check can be forced by clicking on "check for new version" on start screen
* renamed TimePoint to TimeStamp

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src/lib_gui/qt/element/QtCodeFileSingle.h

@@ -7,7 +7,7 @@
 #include <QFrame>
 
 #include "utility/file/FilePath.h"
-#include "utility/TimePoint.h"
+#include "utility/TimeStamp.h"
 
 #include "qt/element/QtCodeNavigateable.h"
 
@@ -52,7 +52,7 @@ private:
 	struct FileData
 	{
 		FilePath filePath;
-		TimePoint modificationTime;
+		TimeStamp modificationTime;
 		bool isComplete;
 		std::string title;