Set orders process turn

Basic form-interface for turn processing.

Didn't quite make it to simulation—there was a hiccup with values being cleared en route to the view that I haven't diagnosed yet. However, the 'finalize' action should give us a sufficiently useful baseline for a API/Javascript proof of concept.

P.S.: Running the feature specs currently throws a swath of deprecation warnings. This is due to the simple_form gem; they have a fix that's been merged to their master branch, but it doesn't look like it's made it to a published gem version yet.

P.P.S: I ended up calling the controller action "finalize" instead of "process" because "process" is an existing method which broke things when I overwrote it.