isVariableInteresting

Whether variable is still relevant to this frame or any of its ancestors (i.e. occurs in relevantGoals, in the goals left of this frame or of an ancestor, or in the query). Used when popping a finished frame back to its parent (in it.unibo.tuprolog.argumentation.core.engine.fsm.StateGoalSelection) to filter the substitution handed up, discarding bindings for variables local to the finished sub-goal.