Add namespace support for the new version of Rosbridge_suite

[FlorianLebecque]

Public API Changes
Add an optional namespace parameter to the Ros class

Description
The roslibjs is broken when setting a namespace to the rosbriduge_suite since this PR on rosbridge_suite.
This change allows dev to set a namespace on the Ros object. This parameter is optional and by default an empty string. When populated, act as a prefix for the different ROSAPI services.

const ros = new ROSLIB.Ros({
    url: props.url
});

ros.namespace = "NAME_SPACE_IN_ROS/";

this allows the Roslibjs to call "NAME_SPACE_IN_ROS/rosapi/Topics" instead of "rosapi/Topics"

[MatthijsBurgh]

The ROS class doesn't have a namespace attribute. So this should be set in the constructor. Also tests should be added so it works with absolute, relative and private namespaces. And I think it requires more parsing than just prefixing the topics/services with the namespace. As you want to be robust against a missing slash at the end of the namespace.

[EzraBrooks]

I'd also appreciate the use of template strings instead of string concatenation here for readability :)

[FlorianLebecque]

I've done change to add the namespace to the constructor.
I've added better logic for 'parsing' of the namespace. this should make it more robust to missing '/' and leading '/'

Unfortunately, I have no idea how to test it, I'am not familiar with javascript testing. Do you have any ressource I could use to add it?

Since testing it requires having multiple rosbridge_suite with different namespaces running on different port for the test.

[MatthijsBurgh]

@FlorianLebecque check CI errors

[FlorianLebecque]

@MatthijsBurgh How can I setup the test to connect to different rosbridge_suite websockets ? To test different namespace configuration ?