Folder system unique entities

Moved code around so that you cannot have two filebases with the same
name in the same sub folder.
Better FileBase

All children of folders can now be accessed via the children class.
Also items with the same parent and same name aren't allowed. Order is
kept the same.
Fixed display and structure

Fixed the necessary controllers and templates to work with the new
entities. Also updated the structure so that collapsable nested folders
are possible.
Little security fix