save/delete handler forms work only when identity property is called "Id" or "ID"

[adamfoneil]

this issue in SqlChartify goes back to this
https://github.com/adamosoftware/SqlChartify/issues/91
in that case, the identity property is WorkspaceUserId, so it doesn't bind in the handler event.

[adamfoneil]

I think the solution may be to update the GridEditor ctor to make the idAccessor arg an Expression so that the property name can be used in the handler form, and model binding should work therefore.