solver for one-class SVM supported

solver for one-class SVM supported
    -add new solver ONECLASS_SVM (-s 21)
    -add function solve_oneclass_svm
    -add new attribute rho to model
    -add new attribute nu to parameter
    -modify function check_parameter, get_decfun_bias
        to reject one-class SVM from accessing bias
    -modify/add function get_decfun_coef, get_decfun_rho, get_w_value
        for one-class SVM to get its decision function
    -add function check_oneclass_model
    -modify python/MATLAB interface and train.c update
    -REDME update