Add afterAll hook

[nonkor]

We have a way to define some common, unrepeatable actions before a group of specs. We need just place the code inside description - it would be run before nested context. Unfortunately, we cannot do something similar as a result action after all nested specs - it would be anyway performed before nested specs.

Let's see an example. Consider, I need only one affiliate for some group of specs - all next action would be about reservations and they do not require re-creation of the affiliate. But if I want to clean up my db modifications after all, there is no way except to create affiliate before each spec and delete it after each spec. With afterAll hook I could escape redundant calls and improve reliability:

describe 'test' spec {
  createAffAPI

  describe 'add reservation' spec {
    //...
  }
  describe 'modify reservation' spec {
    //...
  }

  afterAll { deleteAffAPI }
}

I would even recommend introducing 'beforeAll' hook for consistency and restrict performing any code without wrapping in hooks or specs.