Remove the /nodes directory when deleting a node

Otherwise it might have stale data inside.
Moved role constraints into model and removed edit deployment

(cherry picked from commit ba3fd78c67c85e6702b1d54479f5fe1787f5f52a)
Merge pull request #286 from vuntz/release/roxy/master

Moved role constraints into model and removed edit deployment
Removed the single assignment block from constraints
Merge pull request #287 from tboerger/feature/roxy/fix-constraints

Removed the single assignment block from constraints
Merge pull request #272 from dirkmueller/release/roxy/master

Remove the /nodes directory when deleting a node
Integrated software raid

(cherry picked from commit d86083077ea4e36baa07ee97da62df9c227b1c9a)
Merge pull request #290 from vuntz/swraid-roxy

Backport of software raid to roxy