/**
     * Composes cfg object trying to take values from GET params, using defaults if provided,
     * for most values. Others such as lesson description should not be passed through GET params, due to it's length.
     * @method configFromParams
     * @param {Object} [cfg] Default configuration
     *      @param {String} [cfg.attemptIRI] Needs to be provided if this is a resume attempt action.
     *      @param {String} [cfg.courserIRI] Obligatory if not provided in params.
     *      @param {String} [cfg.courserTitle] Recommended if not provided in params.
     *      @param {String} [cfg.courseDescription] Recommended if not provided in params.
     *      @param {String} [cfg.endpoint] LRS endpoint URL
     *      @param {String} [cfg.auth] Authorization token for the LRS, will be passed in the "Authorization" header.
     *      @param {String} [cfg.lessonIRI] Obligatory if not provided in the params.
     *      @param {String} cfg.lessonTitle
     *      @param {String} cfg.lessonDescription Recommended if not provided in params.
     *      @param {String} [cfg.entry] "ab-initio" or "resume"
     *      @param {Object} [cfg.actor] Obligatory if not provided in params.
     *          @param {Object} cfg.actor.account Recommended if not provided in params.
     *              @param {String} cfg.actor.account.homePage User origin, usually location of the LMS.
     *              @param {String} cfg.actor.account.name User identifier.
     * @return {Object} Config object with parameters fetched form the GET params.
        */
    xAPI.configFromParams = function(cfg){
        var params = getParams();
        cfg.attemptIRI = params.attemptIRI || cfg.attemptIRI;
        cfg.entry = params.entry || cfg.entry;
        cfg.courseIRI  = params.courseIRI || cfg.courseIRI;
        cfg.courseTitle = params.courseTitle || cfg.courseTitle;
        cfg.courseDescription = params.courseDescription || cfg.courseDescription;
        cfg.endpoint = params.endpoint || cfg.endpoint;
        cfg.auth = params.auth || cfg.auth;
        cfg.lessonIRI = params.lessonIRI || cfg.lessonIRI;
        cfg.lessonDescription = params.lessonDescription || cfg.lessonDescription;
        cfg.username = params.username || cfg.username;
        cfg.password = params.password || cfg.password;
        var actor = params.actor;
        if (actor){
            cfg.actor = JSON.parse(actor);
        }
        return cfg;
    }