refactor: use UI file for main window

- main window now use UI file for layout.
- remove all manual computed widget position code. use full Qt layout implementation instead.
- remove useless functions in main window
- change style changed slot as private

app/bottombuttongroup.h

@@ -14,7 +14,10 @@ class BottomButtonGroup : public QGroupBox
 {
     Q_OBJECT
 public:
-    explicit BottomButtonGroup(const std::vector<QAction *> & actionList, QWidget *parent = nullptr);
+    explicit BottomButtonGroup(QWidget *parent = nullptr);
+
+    void addActions(const std::vector<QAction *> & actionList);
+    void addAction(QAction* action);
 };
 
 #endif // BOTTOMBUTTONGROUP_H