Refactors rendering of the CharacterSelector to ng

pain points:
- some convenience functions on backbone.collection would be nice, but 
it's not too hard to refactor to the underscore functional style

cool things:
- scoped ng-repeat="(type, group) in unitGroupings", this is pretty neat
- i like having only to look to the controller and service for where the
data comes from
- template is much easier to parse with all the markup in place
- working with JS simple arrays and objects is really nice