Graph updates are incomplete and delayed

[mgross]

When performing a conservativity check on an edge and the edge is updated, the update is not shown directly afterwards. Instead it gets visible when another action causes a graph update. Additionally when a proof obligation is added to a node, the edge disappears first and reappears with a new graph update.

Steps to reproduce:
- open Hets with Hugo.casl (it is in Hets-lib/ , update your working copy)
- Edit -> Proofs -> Automatic
- Edit -> Unnamed Nodes -> Show nodes
- Select the edge connecting Hugo_E2 and Hugo_E1
- Right click and check conservativity
- Now the edge dissappears and the proof obligation is added to Hugo_E1
- Select the edge from Hugo_E1 to Hugo
- Right click and check conservativity
- Now the edge from Hugo_E2 to Hugo_E1 appears again, but the selected edge disappears

Also when opening Basic/SimpleDatatypes.casl with Hets and doing a Proofs->Automatic, an edge dissappears and Hets terminates which this error: "hets: get: id unknown: 5"

Both behaviours were introduced by changeset:11772.

[maeder]

Redo does not work for Basic/LinearAlgebra_II.casl and Basic/LinearAlgebra_I.casl after Proofs -> Automatic and Undo

hets: DaVinciBasic: graph(mixed_update([delete_edge("gM"),delete_edge("fM"),
...
delete_edge("NM")])) returned error update error: cannot find node or edge with ID GM (to be deleted)

[raider]

fixed by changeset:11792