Implement AppealableArbitrator.sol

[clesaege]

This is a centralized arbitrator who can be appealed to another arbitrator.
The other arbitrator can be any kind of arbitrator.
This contract can inherit from CentralizedArbitrator.

[mahadevan-k]

sent you a pull request on this

[clesaege]

@bitonator 's PR: https://github.com/kleros/kleros-interaction/pull/18/files

[clesaege]

Few comments about how to implement it (but if you have something else which would work that's fine too):
-The Appealable contract must designate another Arbitrator contract for appeals.
-You can get the cost of appeal by asking the other Arbitrator contract.
-After a ruling is made, you need to let some time for parties to appeal, otherwise if you call directly the arbitrable contract, the ruling will be enforced without possibility of appeal.

[mahadevan-k]

Got it, will look into this

[mahadevan-k]

For assigning the Arbitrator contract, I could add an assignDispute method and call it from appealSuccessful, but I'm wondering whether I should add it to AppealableArbitrator or Arbitrator.

Regarding the ruling, I'll move the rule method inside the else clause and add a appealTimeout method which will execute the ruling

[clesaege]

AppealableArbitrator, after an appeal is made, need to transfer the dispute to the appeal arbitrator, so it is in AppealableArbitrator. So AppealableArbitrator must also be Arbitrable.

[0xferit]

Looks like @bitonator gave up. I am starting to work on this.

[clesaege]

You may want to look at #4 as they are quite similar.