Update crowbar_converge to use GET instead of POST.
Flip around keys in HABTM relation for node_roles.

I was building the graph backwards.
Use postgres for everything.
Merge pull request #723 from VictorLowther/pull-req-master-a91d010e6f77c4fc84104247bc7752f73dab5b4d

https://github.com/crowbar/barclamp-crowbar/pull/723

Merged by devtool for cloudedge