Dummy nodes should be allowed in the strategy shown in the GUI

[Manuel Luque]

The evaluation of a decision analysis network (DAN) may need to introduce dummy variables in the strategy (Intervention) to represent an unspecified order of decisions. This kind of variables is used now in the decision tree shown in the GUI. Similarly, the GUI should allowed dummy variables in the strategy. However, in this moment, it throws a org.openmarkov.core.exception.NodeNotFoundException because the artificial variables do not appear in the original DAN. I attach a DAN to reproduce the issue by clicking on the button S.

I suggest to select type of node DECISION for drawing them in the GUI.