Rename node_manager to hammer, and add CLI and API support.

Why hammer?  Because we are using them to beat on the nodes, and it
enables all sorts of late 80s based puns about a certain parachute
pants wearing pop star.
Fix copyright for hammers_controller.
Merge pull request #197 from VictorLowther/add-available-node-manager

Rename NodeManagers to Hammers, and add in needed CLI and API hooks.