rework all currencies

- introduce monero oct 2018 fork as currency `monero`
- remove monero7
- change all dev pools
  - those miner monero7 to handle the fork to monero
  - if the dev pool can not handle the fork to monero the currency is fixed set to `monero` (we can only handle 2 different currencies for user and dev pool)
- remove guards those prevent to use the currency `monero`