Add support to placeUnit for placing a unit on an already existing machine
Added tests for placeUnit functionality in the ecs
Updated deployer changes panel to match designs.
Merge pull request #331 from huwshimi/deployer-bar-visuals

Updated the deployer changes panel to match the visuals (https://drive.google.com/a/canonical.com/?usp=folder#folders/0B7XG_QBXNwY1WGlyVzN2LWtrcmM)

QA:
Drag a service to the canvas.
Click the "2 changes" link in the deployer bar.
Check that the panel matches the visuals.
Merge pull request #334 from hatched/unplaced-to-existing

1. Fixes a bug with `ecs.placeUnit` which would cause dropping an unplaced unit on an existing container to fail.
2. Adds tests for `ecs.placeUnit`.

#### To QA
- Open `config-debug.js` and disable `simulateEvents`.
- Open `app.js` and add `this.fakebackend = state` after line 418
- Load the GUI using the mv and il flags.
- Drag and drop a charm to the canvas. 
- Switch to the machine view.
- Drag and drop the unplaced unit to the `New Machine` header.
- Click `deploy` and `confirm`.
- Switch back to the service view.
- Run `app.db.machines.add({id: '0/lxc/0'}); app.fakebackend.db.machines.add({id: '0/lxc/0'})` in the console.
- Drag and drop a new charm to the canvas.
- Switch to the machine view.
- Select the `0` machine. You should now see an empty container and 'Bare Metal' with your previous service.
- Drag the unplaced unit and drop it on the empty container.
- Click `deploy` and `confirm`.
- Switch to service view and back to machine view. You should now have placed your new service on that container.