MVP example for model validation every N training steps

[pdogra89]

-Depends on task 2

• Minimal evaluation metrics interface (or using ignite.metrics?)
  -Event handler for model validation and early stopping

[Nic-Ma]

Hi @madil90 ,

I already submitted PR #66 to support mean_dice metric, could you please help add the validator handler and early-stop for training example based on ignite?
Thanks in advance.

[madil90]

Sure. I can add these over the weekend.

[Nic-Ma]

Hi @madil90 ,

Thanks, I also update the PR to support both multi-labels and multi-classes outputs.