Integrated customizable bash prompt

Get a nice configurable shell prompt for all nodes... YEAH!
This is a followup pull request after discussion on https://github.com/crowbar/barclamp-deployer/pull/219
@vuntz Out of curiosity what's the problem when doing copy&paste?

@tboerger If you read http://json.org/ carefully you will see that @vuntz is right - `\/` is allowed but so is `/`, so there is no requirement to escape `/`.  So the correct thing to do would be to adjust the comment according to his suggestion by not escaping `/` - that way we get the formatting fixed *and* there is no copy&paste issue.  That gives us the best of both worlds.