turn actions arguments into a payload and remove callback

[tarmann]

Quite often we have to send more than one param to the actions and this can get quite messy.

Also, we are not using the callback as we intended in the beginning.

So instead of:

  doSomethingTask: task(function * (store, callback, model, param1, param2){
    updatedModel = yield doSomething(model, param1, param2);
    return { callback, model: updatedModel };
  })

We can have:

  doSomethingTask: task(function * (store, payload){
    response = yield doSomething(model, payload[0], payload[1], payload[2]);
    return response;
  })