New and improved fault management

This introduces the concept of "channel". Presets may belong to different
channels such that if one preset causes a fault, only presets belonging
to the same channel will be paused. Presets in other channels will continue
to be applied.

lib/cache.coffee

@@ -141,7 +141,7 @@ refresh = (callback) ->
               else
                 throw new Error("Unknown configuration type #{c.type}")
 
-          presets.push({name: preset._id, schedule: schedule, events: events, precondition: precondition, provisions: _provisions})
+          presets.push({name: preset._id, channel: preset.channel or 'default', schedule: schedule, events: events, precondition: precondition, provisions: _provisions})
 
         if -- counter == 0
           computeHash()