Explore publishing topic from client

[AWatk]

No description provided.

[AWatk]

This is an enhancement that touches on nearly every component of rosmct

OpenMCT Client

Create a text input box for each topic field and a Publish button.
Encapsulate into a json object and send over the websocket with a format similar to openmct's subscribe/unsubscribe requests. i.e. ws.send("publish " + JSON.stringify(topicMessage)

RealTimeServer

add an additional request handler for the publish command that passes the message to publish on to the Ros System via a callback (see next section)

Ros System

define a callback that is passed around in the same way as the subscribe/unsubscribe callback currently is that takes in a message object and publishes it using roslib.js