logic: Improved code view performance

* Don't set stylesheet for every token activation
* Streamlined code area creation steps
* Delay most syntax highlighting until lines become visible

src/lib_gui/qt/view/QtCodeView.h

@@ -41,8 +41,6 @@ public:
 	virtual bool isInListMode() const;
 	virtual bool hasSingleFileCached(const FilePath& filePath) const;
 
-
-
 private:
 	void performScroll();
 	void setStyleSheet() const;