Optimize noderole graph traversal.

This adds a view that recursivly expands node_role_pcms, and fixes up
all the instances where we were walking all the parents or children of a
noderole to use that view instead of recursion on the Ruby side plus a
bunch of unneeded queries to the database.
Flesh out wanted_attr handling.

Allow the role to declare where wanted attribute data should be put when
the jig infrastructure is building an attribute blob to pass to a
jig. It will default to the same location that the wanted attrib gets
its data from in the first place.
Merge pull request #827 from VictorLowther/pull-req-master-435923b0a0746ceaecb6283577ca9f9f79e1be4a

https://github.com/crowbar/barclamp-crowbar/pull/827

Merged by devtool for VictorLowther