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/network/QtUpdateChecker.h

@@ -0,0 +1,15 @@
+#ifndef QT_UPDATE_CHECKER_H
+#define QT_UPDATE_CHECKER_H
+
+#include "UpdateChecker.h"
+
+class QtUpdateChecker
+	: public UpdateChecker
+{
+public:
+	static void check(bool force = false);
+
+	virtual void checkUpdate() override;
+};
+
+#endif // QT_UPDATE_CHECKER_H