supporting catkin packages

Now rosnodejs does not support catkin packages (catkin is a new package manager introduced from groovy).

Catkin packages have package.xml like manifest.xml, so we need to check package.xml as well as manifest.xml.

test code:

```javascript
var packages = require("./lib/packages");
packages.findPackage("roscpp", function(err, pack) { console.log(err); console.log(pack);});
```

```sh
echo $ROS_DISTRO
> groovy
ls `rospack find roscpp`
> cmake  msg  package.xml  rosbuild  srv```