Determine if the selected variables in a BMA step represent a new model
[j,visits] = find_new(binsave,vinew,visits,nvar,conv)
* vsave = matrix containing all models selected
* vinew = vector of current model specification
* visits = matrix containing # of visits to each model
* j = position in the list of models of the current model
* visits = updated matrix containing # of visits to each model