Ability to set Page/Folder permissions#86

When I want to set the permissions of a page or folder

I want to be able to do it from the drop down menu

So I can quickly set the permissions

This ticket covers being able to set permissions for a folder or page instead of the whole wiki.

Note that it is possible to set incremental permissions by setting the folder or doc permissions in Drive, but when inviting a new user that user will get access to the entire wiki, and it will be required to set the permissions again to remove them.