Implement sharing folders functionality

[mrnicegyu11]

User story:

As a user...

... I want to be able to group projects into folders, and nested folders, for my own organization of the dashboards
... I want to be able to share individual projects with selected organizations/users
... I want to be able to create shared-folders. All projects' sharing/permission in these special shared folders are overwritten by the shared-folder's permissions. I can create regular folders (for structuring the work) inside the shared folder. I can only create shared-folders at the top-level of the dashboard.
... I can convert a top-level regular-folder into a shared folder. I am informed/alerted about the sharing permission change of the individual projects.
... I can convert a shared-folder to a regular folder (unsharing).
... I can delete regular and shared folders
... I can move subfolders out of shared folders (to the top-level); these will loose all sharing properties; the users will be informed appropriately