Include smart-notifier in Ubuntu by default

Binary package hint: ubuntu-desktop

The "smart-notifier" package (and its dependency, smartmontools) should be included and configured in Ubuntu by default. These packages monitor the S.M.A.R.T. health reporting system that is present in most hard drives and can notify the user of impending failures before they occur. This is a valuable subsystem to have and setting it up should not be left up to the user.

Note that for this to happen, changes will probably be necessary to the packages themselves: smartd's configuration is not very automatable, and smart-notifier's UI is not very Ubuntuish.