> The Spider Objects

>        CV cross validation object

>         a=cv(algo,hyperParam) Returns a cv object on algorithm algo using with
>                               given Hyperparameters.

>         Possible hyperparameters (with defaults):
>          folds=5               - number of folds
>          repeats=1             - can do n*CV for reduced variance
>          balanced=0            - determines if cv shall be balanced  (same number of
>                                   positives in each fold)
>          store_all=1           - determines if models trained in all folds shall be stored
>          output_train_error=0  - determines wheter to output training error on each fold
>                                   (else cv error, i.e  test left out fold as default)
>          train_on_fold=0       - determines to  test on left out fold and train on the
>                                   rest (set to true for the opposite).
>          store_trialbytrial=0  - whether to store the field a.trialbytrial, the rows of
>                                   which are [i, foldnumber, y_i, f(x_i)] for each index
>                                   i of a data point on which the algorithm was tested

>         Model:
>          child                 - stored in child algorithm

>         Methods:
>          train                 - selfexplanatory
>          test                  - selfexplanatory