WIP: Update service icons on a machine.

Right now the current code is a bit ugly and there are no tests. That said, I wanted to get a PR out there to validate my approach and get feedback on ways to clean things up.

### QA

With `/:flags:/il/mv`.

1. Deploy the Wikimedia bundle.
2. Drag-n-drop the Wordpress charm over, but don't deploy it.
3. Switch to machine view.
4. Run this in your console:
~~~~
var u = app.db.units.item(2), m = app.db.units.revive(u); m.set('machine', '0');
~~~~

You should see the Wordpress icon added to the 0 machine.