Box.com: Fix navigation and content loading

This merge request brings a fix to the Box.com navigation with:

• The item ID that is now set as the current path which fixes the directory navigation.
• The go back action that now triggers a query that retrieves the parent folder ID in order to load the correct content.
• The refresh action that does not duplicate the displayed content anymore.

Closes #776 (closed)

This merge request also fixes the content loading that is now properly displayed right after the user successfully authenticates to the service.

Closes #1516 (closed)