Update service icons on a machine.
Consistent API for DB event handling.
Eliminating dupe tests.
Refactor the deployer view to easily add changes version of summary.
Merge pull request #320 from kadams54/machine-service-icons

### 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.
Show recent list of changes in the summary panel.
* The changes button pops up the summary panel with the recent changes.
* When the panel is open, the changes button closes the panel.
* Deploy confirmation summary info is _not_ shown when the recent changes are shown.
* Likewise recent changes are not shown when the confirmation is up.
Merge branch 'develop' of github.com:juju/juju-gui into develop