* [shared dir view] redesigned it
- changed to a full-screen 'side panel & main panel' layout
- added a 'folder tree' panel, a current path bar with an operation dropdown
menu, a toolbar for selected items, a 'view mode' menu, and a 'sort'
menu
* [shared dir view] added a resizing bar (enable users to resize the width of side panel and main panel)
* [shared dir view] path bar: added a 'plus' icon to the dropdown menu toggle when 'upload' is offered in the menu
* [shared dir view] folder tree: cleaned up the code
* [shared dir view] improved 'visit a folder'
* [shared dir view] improvements & cleanup
