supersites should expand tree collection

[KitWallace]

supersites need to be fully implemented - when selected, the tree list should be composed of the tree lists of the component sites ? how deep

collections already work like this

[KitWallace]

collection hierarchy is the reverse of the site hierarchy but uses containment rather than reference so also restricted to a single hierarchy

in general top down with references allows for multiple hierarchies
bottom up supports only one
topdown requires multi-valued children whereas bottom up requires only single valued parent - so better for CSV implementation

[KitWallace]

done - will be useful for tynesfield structure

[KitWallace]

but not solved for search

[KitWallace]

select-trees-by-sitecode handles heirachical sites now