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/QtCodeFile.h

@@ -18,7 +18,7 @@ class QtCodeFileTitleButton;
 class QtCodeNavigator;
 class QtCodeSnippet;
 class QVBoxLayout;
-class TimePoint;
+class TimeStamp;
 
 class QtCodeFile
 	: public QFrame
@@ -29,7 +29,7 @@ public:
 	QtCodeFile(const FilePath& filePath, QtCodeNavigator* navigator);
 	virtual ~QtCodeFile();
 
-	void setModificationTime(const TimePoint modificationTime);
+	void setModificationTime(const TimeStamp modificationTime);
 
 	const FilePath& getFilePath() const;
 	std::string getFileName() const;