Improvements Failed Contract Distributions

Todo

• Rename db table distributions -> failed_distributions
• Rename db columns
  retries -> attempts
last_retry_at -> last_attempt_at
next_retry_at -> next_attempt_at
  This makes more sense when you look from the UI, where we also display 'attempts' on the Distribution detail page.
• Rename ContractDistributionService -> DistributionService since it distributes both contracts and signatures
• Move exponential backoff logic from the PeerCommunicationService to the ContractDistributionService. The ContractDistributionService can use the PeerCommunicationService to send the contracts. The DistributionService can have better readable method names then. Eg. DistributeContract, DistributeSignature instead of UpdateWithLastAttempt or UpdateNewAttempt.
• Disable manual resend buttons when next_retry_at is not empty
• Review translations for the resend distribution confirmation modal
• Also display time in the UI for the next attempt at (only the date is not sufficient enough)
• Prevent multiple concurrent retries for the same distribution. Introduce lock?

Issue: #217 (closed)