CTL query dialog - allow only DFS for CTL queries

[Jiri Srba]

As it is now, the CTL query dialog allows all four search strategies even for queries
that are not reachability queries. The behaviour should be as follows:

If the query is reachability, then all four search strategies should be possible to select in the GUI.

If the query is not reachability query, enable only DFS and heuristic search (the is correctly detected for traces already, as they are disabled as soon as the query is not reachability).
The other two options should be in gray.

[Jiri Srba (srba)]

Now thinking about this, it is probably ok as if the query gets reduced to reachability query then e.g. BFS could be used too ... not sure what to do, perhaps no fix is needed or any other suggestions?

[Jiri Srba (srba)]

Well, the help actually explains this already well, so I guess nothing should be changed. The only problem is that in the tooltip for mouse over the Heuristic search strategy says that if not available, it becomes BFS but it should say DFS instead. This can be fixed directly in the ctl-branch. The rest is ok as it is.