Currently, `git annex status` only shows the size of 1 copy of each file.
If numcopies is being used for redundancy, much more disk can actually be
in use than status shows.

One idea:

	known annex size: 2 terabytes (plus 4 terabytes of redundant copies)

But, to get that number, it would have to walk every location log, 
counting how many copies currently exist of each file. That would make
status a lot slower than it is.

One option is to just put it at the end of the status:

	redundancy: 300% (4 terabytes of copies)

And ctrl-c if it's taking too long.

Hmm, fsck looks at that same info. Maybe it could cache the redundancy
level it discovers? Since fsck can be run incrementally, it would be tricky
to get an overall number. And the number would tend to be stale, but
then again it might also be nice if status shows how long ago the last fsck
was.
