src: refactored UI elements and graphics file structure

* split QtIconButton into multiple files
* moved graph elements from view to graphics
* structured elements into sub directories

src/lib_gui/qt/element/button/QtHoverButton.h

@@ -0,0 +1,23 @@
+#ifndef QT_HOVER_BUTTON_H
+#define QT_HOVER_BUTTON_H
+
+#include <QPushButton>
+
+class QtHoverButton
+	: public QPushButton
+{
+	Q_OBJECT
+
+public:
+	QtHoverButton(QWidget* parent = nullptr);
+
+signals:
+	void hoveredIn(QPushButton*);
+	void hoveredOut(QPushButton*);
+
+protected:
+	void enterEvent(QEvent *event);
+	void leaveEvent(QEvent *event);
+};
+
+#endif // QT_HOVER_BUTTON_H