airspec: Support injection at before/beforeAll

[xerial]

class A extends AirSpec {
  override protected def design = newDesign.bind[X].toInstance(x)

  private var x:X;
  protected def beforeAll(x:X) { this.x = x }

  def test = {  
     // use x 
  }
  def test2 = {
     // use x
  }
}

[xerial]

@shimamoto Does this work for your use cases?

[xerial]

I'll close this ticket in favor of the new test(..., design = ...) syntax #876