Docs faq 348

Resolves: https://github.com/ClusterHQ/flocker/issues/348

Particularly interested in @lukemarsden feedback since he is hearing these questions all the time.
@itamarst I understand what you are saying, but this is a frequently asked question when we talk to people what what are are building over the short term.  In particular, this question came out of the database cloning user story that Luke and I validated with some docker users.  When we have this feature, but call it something else, we can adjust the wording. Or if we ultimately decide not to build it, we can remove it.  I'd like to keep it in here though so we can point people to it when the question comes up.