Better slider to set size of server backing volume

When a user is creating a volume-backed server, they see this:

It's difficult to specify a precise size because that little slider goes all the way from 2 to like 1000. If I wanted to create a 2 TB volume it would be a bad time. So, we need a better widget. :) We should probably allow numeric text input instead of (or in addition to) the slider.

(We already do this for the volume creation view:)

We should clamp the maximum size of the volume to whatever will succeed given the user's current volume quota.