isVariableInteresting

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