Alternative syntax for create Topics, Services, Params, etc

Simple patch to make creating topics, services, params and clients less verbose

```js
var ros = new ROSLIB.Ros({
    url : 'ws://localhost:9090'
});


var maxVelX = new ROSLIB.Param({
    ros : ros,
    name : 'max_vel_y'
});

// After this patch
var maxVelX = ros.Param({
    name : 'max_vel_y'
});
```