feat: modify pienapple-picture with my remix

- change UI layout to make it looks like the default style of Windows image browser.
- update icons to material design icon for better looks. add lost icons for those new added button at the bottom bar.
- restore window style to normal. remove borderless style.
- delete X button at the right-top corner. disable feature that drag window to move, because all functions provided by native window are restored.
- move prev next image button to the center of bottom bar.
- move navigator view to the right-bottom corner so that it will not overlay on the shown image.
- remove all animation effect, including alpha transition, fade out when exiting and etc.
- delete function that double click windows to exit. now double clicking windows will do nothing. change default value of double click behavior to do nothing.
- change default value of stay on top to false because stay on top is not the default behavior of Windows image browser.

app/mainwindow.h

@@ -51,11 +51,6 @@ public:
 
 protected slots:
     void showEvent(QShowEvent *event) override;
-    void enterEvent(QT_ENTER_EVENT *event) override;
-    void leaveEvent(QEvent *event) override;
-    void mousePressEvent(QMouseEvent *event) override;
-    void mouseMoveEvent(QMouseEvent *event) override;
-    void mouseReleaseEvent(QMouseEvent *event) override;
     void mouseDoubleClickEvent(QMouseEvent *event) override;
     void wheelEvent(QWheelEvent *event) override;
     void resizeEvent(QResizeEvent *event) override;
@@ -119,19 +114,11 @@ private:
     ActionManager *m_am;
     PlaylistManager *m_pm;
 
-    QPoint m_oldMousePos;
-    QPropertyAnimation *m_fadeOutAnimation;
-    QPropertyAnimation *m_floatUpAnimation;
-    QParallelAnimationGroup *m_exitAnimationGroup;
     QFileSystemWatcher *m_fileSystemWatcher;
-    ToolButton *m_closeButton;
-    ToolButton *m_prevButton;
-    ToolButton *m_nextButton;
     GraphicsView *m_graphicsView;
     NavigatorView *m_gv;
     BottomButtonGroup *m_bottomButtonGroup;
     bool m_protectedMode = false;
-    bool m_clickedOnWindow = false;
 };
 
 #endif // MAINWINDOW_H