Lusas_Toolkit: Detect HOFs when deleting elements

[peterjamesnugent]

When deleting points, the method should recognise when a point is part of a higher order feature (such as a line or surface) and return a warning.

We could probably do this in a single Linq query and group in to one warning.

e.g. "P1, P2, P3 and P4" define higher order features and therefore cannot be deleted.

The same would go for lines, and it will not be too difficult for surfaces (if solids are implemented).

[peterjamesnugent]

Maybe as an interim solution we raise a warning when this is the case (the deletes are generally not implemented).