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/api-functions.coffee

@@ -242,8 +242,9 @@ deleteDevice = (deviceId, callback) ->
     return callback(err) if err
     db.devicesCollection.remove({'_id' : deviceId}, (err) ->
       return callback(err) if err
-      db.redisClient.del("#{deviceId}_presets_hash", "#{deviceId}_inform_hash", (err) ->
-        callback(err)
+      db.faultsCollection.remove({'_id' : {'$regex' : "^#{common.escapeRegExp(deviceId)}\\:"}}, (err) ->
+        return callback(err) if err
+        db.redisClient.del("#{deviceId}_presets_hash", "#{deviceId}_inform_hash", "#{deviceId}_faults", "#{deviceId}_no_tasks", callback)
       )
     )
   )