Error summary at the end of each test & campaign 


I'm counting errors and failures on the slave, perhaps this should be done in `json-report` instead? But this seemed a bit strange for me, it would require augmenting the `event` on-the-fly when it arrives to the `json-report` before it is dispatched to `console-report`. I checked and it works but seems hacky to me.

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Here's the preview of updated logging (the first error is actually an issue with Attester itself after recent refactoring):

![preview](https://f.cloud.github.com/assets/1437027/901133/a2163b50-fb77-11e2-9c58-9be4da2c2e8d.png)

I think we could also remove the `browserName` from the event and get it in the same way as `browserRemainingTasks`.