Store/data (#13): rewrite ungroup_nodes for basic scenarios; decompose...

Store/data (#13): rewrite ungroup_nodes for basic scenarios; decompose group_nodes in insertLink; wip: remove_nodes, removing original entries sets isRemoved (changed dataset specs); remove gettter for new Id (should not be public)

Remove error in dataset-harry.

BaseIcon: compute radius.

Node/link: show alert when trying to render with invalid id.