Show workers with their status, and allow clicking on a worker to activate
it and show its details (which currently is limited to just its ID). Does
include Vue Router handling of the active worker ID and CSS classes for
worker statuses.
This basically copies the `JobsTable` component to `workers/WorkersTable`.
The intention is that all the jobs-specific components will move into a
`jobs` subdirectory at some point.
Most of the code moved from `App.vue` to `views/JobsView.vue`.
Notification bar has its own component, and there are placeholder
"views" for Workers and Settings pages.
There is still some clunky handling of updates via SocketIO, as those
are a mix of job-specific and global (like SocketIO reconnection
events). The advantage of the current approach is that SocketIO
connections are closed when you leave the Jobs page, and reopened when
you enter the Workers page. My gut feeling says this is nice because it
ensures that all SocketIO connection-specific things are cleaned up when
you navigate.
