…endencies

The plugin is relying on a timer that triggers a full refresh every second.
This impacts UI responsiveness and increase resource usage.
The UI script also uses a timer to figure out when the d3 library has finished loading.

This commit addresses both issues by:

* Replacing the first timer by a poll mechanism. When the API notifies
  on a change, a model change is added to a queue. The ui checks the queue
  for new updates and apply them. This allows for a cleaner execution model
  and improves responsiveness.

* Using extra-scripts to bundle ui & d3 with webpack. This removes the
  second timer and have the side benefit of reducing the plugin's size by
  5 due to treeshaking.