document need to deploy couch node before webapp node

The webapp creates design documents on the couch when it's deployed. If the couch gets deployed again these will be cleared. So the webapp needs to be deployed afterwards to work. We'll fix this in the long run but for now this needs to be documented.

I don't know where to put it best though.

(from redmine: created on 2013-09-06, closed on 2013-11-12, relates #4460 (closed))