> The Spider Objects

>       GRIDSEL model selection object via grid search

>        A=GRIDSEL(A,H) returns a gridsel object initialized with
>        algorithms A and hyperparameters H.

>        Finds the best of the algorithm from the set A, and trains
>        and stores that model.

>        Hyperparameters.

>         a.child=A                -- methods to evaluate
>         a.loss='class_loss'      -- loss measure to use
>         a.score=cv('folds=5')    -- method of evaluating algorithms

>        Model
>         a.scores=[]        score of all of methods tried
>         a.best_score=[]    score of best methods tried
>         a.best_index=[]    index of best methods tried
>         a.best=[]          learnt model of best method tried

>        Example:
>          train 3 svms with C=1,2,3 and validate with 3 fold cross validation
>        [r,a]=train(gridsel(param(svm,'C',[1,2,3]),{'score=cv;score.folds=3'}),gen(toy)) ;

>        Methods:
>         train, test