Wires up the slot ordering arrows to move units

pain points:
- is passing around the indexes ugly?
- having to pass indexes instead of having an abstraction to snag the
index of a unit in Units is kind of ugly… would be nice to have a unique
identifier for a model other than the internal $$hashKey
Reworks basics of showing/hiding stat editor

This is probably not ideal, using a service to manage the app state to 
determine whether the user is editing a unit or not, but I opted for it
over storing a unit.editing flag because I don't want app state to leak
into the models and then have to prune keys if/when saving would happen.

pain points:
- forgetting to uncomment the manual show/hide state management in the
stylesheet; backbone was using this and i thought things was broke for
quite a while before realizing :(
- $rootScope.$broadcast from a service wasn't initially aware, but I 
suppose this is similar to broadcasting events on Backbones global
Backbone.Event bus
- naming: AppStateService? TransitionService? UIControlService? no idea
what to call this thing :P