[Kst] branches/work/kst/kst1kde4/kst/src/libkst

[Brisset, Nicolas]

> The user experience question is - should we let the user delete bottom
up
> (in which case they might very well make a Big Blunder (TM) and delete
> something important) or make them delete top down (which is safe, but
possibly tedious).
> 
> Kst 1.x did the latter, and I never minded it, since there was a
'purge'
> convenience function in the data manager to delete anything that was
> unused.
> 
> Kst2 currently does the former.
I see various options to handle object deletion:
1) bottom-up deletion but then with protections: i.e. when the user
deletes a vector or other primitive, a popup shows the list of
dependents if any and in that case asks for confirmation
2) top-down, aggressive deletion: when some objects are deleted, all
objects that it frees (i.e. vectors used only in the deleted curve, etc)
are deleted
3) top-down, lazy deletion: the kst 1.x way. You can trigger a cleanup
of unused objects, but it has to be done manually