Recent panel scale mode & lefty mode

* Add scale mode:
    Allow user to scale recent panel size down.
* Add lefty mode:
    Allow recent panel to show up on the left edge
    instead of the right edge for left handed people.

最近应用面板 缩放模式&左利手模式

* 添加缩放模式:
    允许用户缩小最近应用面板尺寸.
* 添加左利手模式:
    允许最近应用面板从左侧出现(而不是从右侧),
    方便左利手用户操作.

Thanks to SlimRoms for the original implementation.
感谢SlimRoms原创实现此功能.