bug with renaming an inherited variable in all_variables

[borning]

Suppose you have a list of variables in all_variables. Everything in the list is inherited from a parent. You want to rename a variable. So you click on it to make it editable, and rename it. At that point you no longer see the old inherited version.

However, in reality the inherited variable with the old name can still be accessed. Further, if you save the xml and restart the gui later, the old variable will be listed (greyed out) in all_variables.

To fix this, after the rename, we should either

1. Immediately add the greyed-out inherited variable back into the list in the GUI.
2. Implement a new "deleted" node type, which serves to mask off an inherited node. When you do the rename, you add the old variable back to the list as a "deleted" node to indicate that the inherited variable is no longer to be in the list. This still needs to show up in the XML display, perhaps using strike-out text (since otherwise the user may be very puzzled).

For all_variables, there is not much harm in having both the old and new variables in the list -- but we should discuss this.

Another place something like this can arise is in the list of variables to use in a model. These are in a selectable list with Use/Skip values. A similar problem arises if you make an inherited item editable. However, in this case we should replace the whole Use/Skip design with a popup menu or the like with a selection list. (This will be the subject of a more elaborate ticket, later.)

Is there anyplace we do really need the "deleted" functionality?