Rename DefaultOrderFundsCalculator to DefaultExchangeFundsCalculator
Merge pull request #162 from sortega/corner_cases

Resubmit step signatures and payment proofs on micropayment channels
Group deposits and refunds at Exchange.Amounts

And remove the Role methods that get outdated thanks to this.
Make BitcoinFeeCalculator a trait and simplify its methods
Introduce StepAmounts to represent the amounts exchanged on one step
Rename OrderFundsCalculator to ExchangeAmountsCalculator

And method calculateFunds to amountsFor
Introduce Role.fromOrderType
Distinguish between amounts exchanged and required
Unnecessary expression
Rename field on AmountsComponent
Use an amounts calculador for order actor and integration tests
Make HandshakeArbiterActor use an amounts calculator
Remove setting coinffeine.hardcoded.intermediateSteps
Promote Amounts.deposits to a member variable
Promote Amounts.refunds to a member variable
Introduce per-step amounts in Exchange.Amounts
Remove the assumption of same-sized steps

Except from the exchange amounts calculator, obviously.
Make Amounts.steps an attribute instead of being calculated

And drop from attributes to calculated values bitcoinExchanged and
fiatExchanged.
Fix risizing on operations view
Add Coinffeine icon to GUI