Component allowing to select folders in a tree hierarchy.

Folder tree checkbox selection is quite common:

• When selecting a parent, all its children are recursively selected as well
• When unselecting a parent, all its children are recursively unselected as well
• When selecting a child, all its parent are recursively marked as indeterminate
• When selecting all children, the parent is automatically selected
• When unselecting all children, the parent is automatically unselected

Folder tree selection event is a bit specific in its behavior though:

• when selecting a folder without children, it is emitted in the selection
• when selecting a folder A which has children, all the children are selected but the selection event will contain only the folder A id
• when selecting a folder A which has children and then unselecting one child, the selection event will not container folder A id, but it will contain the remaining selected child ids.