Hotfix deploy & pretty output

Two changes:

1. Allow a hotfix deploy. Ahotfix deploy is similar to a normal deploy, except:

- the maintenance page is not shown
- db migrations are not run
- load notifications are not run

The app remains available until the deploy is completed, at which point the symlink is moved and Passenger restarts the app.

2. Allow pretty output. Suppresses the default verbose output and gives the pretty. The old verbose mode can be enabled with the `verbose=true` env var.