[Utopia] Removable devices and write-caching

[John <jsk29 cornell edu>]

I've got a quick suggestion for removable devices, but it will
be a challenge to implement well:

Write-cache, but if a device is yanked out while there is data
in the cache, alert the user.  The user can choose to reinstall
the device or throw away the data in the cache.

Later,
John