add create to the spec

I suspect we may actually want to support --ephemeral, but it's too
late at night to think through the cases of that (i.e. I assume we'd
only want persistent ephemeral containers, and in that case is it
worth having them).  So here's the basic blurb.

Changelog 201411070156:
 1. remove the 'copy' command as it is superfluous
 2. remove the sentence fragment about applying profiles to existint
    containers.
 3. update the 'start' description.

I don't think I managed to capture what Stéphane wanted me to say about
start being like create with also starting, but since it doesn't always
create I wasn't sure how to do it.  I do think my update makes it just a
bit claerer than it was.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>