[kplato] delete node

[Heiko Evermann]

Hi it's me again.

I just could not bear it any longer and I added a "delete node" to the 
popup menu and implemented it. It seems to work quite well.

The only drawback is that it deletes the current node of the gantt-view. 
This means: if you pick "menu/add task" without picking any other node 
before,
you get a crash, as the current node of the gantt-view no longer exists. 
I spent some time looking how to reset this current node to the parent 
or to the next sibling of the deleted node, but this was not successful.

Any ideas how to reset the current node in gannt/pert-view?

Heiko